diff --git a/admin/cli/automated_backups.php b/admin/cli/automated_backups.php
index dc80c7aedc10..3c3841e718d1 100644
--- a/admin/cli/automated_backups.php
+++ b/admin/cli/automated_backups.php
@@ -75,8 +75,7 @@
     $DB->set_debug(true);
 }
 if (!empty($CFG->showcrondebugging)) {
-    $CFG->debug = DEBUG_DEVELOPER;
-    $CFG->debugdisplay = true;
+    set_debugging(DEBUG_DEVELOPER, true);
 }
 
 $starttime = microtime();
diff --git a/admin/cli/install.php b/admin/cli/install.php
index 21617cf0860c..fcd25b248fa9 100644
--- a/admin/cli/install.php
+++ b/admin/cli/install.php
@@ -162,6 +162,9 @@
 $CFG->early_install_lang   = true;
 $CFG->ostype               = (stristr(PHP_OS, 'win') && !stristr(PHP_OS, 'darwin')) ? 'WINDOWS' : 'UNIX';
 $CFG->dboptions            = array();
+$CFG->debug                = (E_ALL | E_STRICT);
+$CFG->debugdisplay         = true;
+$CFG->debugdeveloper       = true;
 
 $parts = explode('/', str_replace('\\', '/', dirname(dirname(__FILE__))));
 $CFG->admin                = array_pop($parts);
diff --git a/admin/tool/generator/cli/generate.php b/admin/tool/generator/cli/generate.php
index 4514fd7cea87..353883e1d300 100644
--- a/admin/tool/generator/cli/generate.php
+++ b/admin/tool/generator/cli/generate.php
@@ -28,7 +28,7 @@
 require(dirname(__FILE__) . '/../../../../config.php');
 require_once(dirname(__FILE__) . '/../locallib.php');
 
-if (!debugging('', DEBUG_DEVELOPER)) {
+if (!$CFG->debugdeveloper) {
     echo("This script is for developers only!!!\n");
     exit(1);
 }
diff --git a/admin/tool/generator/index.php b/admin/tool/generator/index.php
index f77c8e0e1af6..7a917e91bae3 100644
--- a/admin/tool/generator/index.php
+++ b/admin/tool/generator/index.php
@@ -34,7 +34,7 @@
     error('Only for admins');
 }
 
-if (!debugging('', DEBUG_DEVELOPER)) {
+if (!$CFG->debugdeveloper) {
     error('This script is for developers only!!!');
 }
 
diff --git a/admin/tool/phpunit/webrunner.php b/admin/tool/phpunit/webrunner.php
index f697f7ee085c..f52bf6b002ea 100644
--- a/admin/tool/phpunit/webrunner.php
+++ b/admin/tool/phpunit/webrunner.php
@@ -34,7 +34,7 @@
 navigation_node::override_active_url(new moodle_url('/admin/tool/phpunit/index.php'));
 admin_externalpage_setup('toolphpunitwebrunner');
 
-if (!debugging('', DEBUG_DEVELOPER)) {
+if (!$CFG->debugdeveloper) {
     error('Not available on production sites, sorry.');
 }
 
@@ -82,7 +82,7 @@
         if ($code != 0) {
             tool_phpunit_problem('Can not initialize database');
         }
-        $CFG->debug = 0; // no pesky redirect warning, we really want to redirect
+        set_debugging(DEBUG_NONE, false); // Hack: no redirect warning, we really want to redirect.
         redirect(new moodle_url($PAGE->url, array('execute'=>1, 'tespath'=>$testpath, 'testclass'=>$testclass, 'sesskey'=>sesskey())), 'Reloading page');
         echo $OUTPUT->footer();
         die();
@@ -103,7 +103,7 @@
         if ($code != 0) {
             tool_phpunit_problem('Can not initialize database');
         }
-        $CFG->debug = 0; // no pesky redirect warning, we really want to redirect
+        set_debugging(DEBUG_NONE, false); // Hack: no redirect warning, we really want to redirect.
         redirect(new moodle_url($PAGE->url, array('execute'=>1, 'tespath'=>$testpath, 'testclass'=>$testclass, 'sesskey'=>sesskey())), 'Reloading page');
         die();
 
diff --git a/auth/cas/cli/sync_users.php b/auth/cas/cli/sync_users.php
index 33cf33abbce3..a02c32f16c32 100644
--- a/auth/cas/cli/sync_users.php
+++ b/auth/cas/cli/sync_users.php
@@ -48,7 +48,7 @@
 require_once($CFG->dirroot.'/course/lib.php');
 
 // Ensure errors are well explained
-$CFG->debug = DEBUG_NORMAL;
+set_debugging(DEBUG_DEVELOPER, true);
 
 if (!is_enabled_auth('cas')) {
     error_log('[AUTH CAS] '.get_string('pluginnotenabled', 'auth_ldap'));
diff --git a/auth/ldap/cli/sync_users.php b/auth/ldap/cli/sync_users.php
index ee155384962d..6898293a2e9f 100644
--- a/auth/ldap/cli/sync_users.php
+++ b/auth/ldap/cli/sync_users.php
@@ -52,7 +52,7 @@
 require_once($CFG->dirroot.'/course/lib.php');
 
 // Ensure errors are well explained
-$CFG->debug = DEBUG_NORMAL;
+set_debugging(DEBUG_DEVELOPER, true);
 
 if (!is_enabled_auth('ldap')) {
     error_log('[AUTH LDAP] '.get_string('pluginnotenabled', 'auth_ldap'));
diff --git a/backup/util/factories/backup_factory.class.php b/backup/util/factories/backup_factory.class.php
index e2143cd05e9a..6f8ba31d0c82 100644
--- a/backup/util/factories/backup_factory.class.php
+++ b/backup/util/factories/backup_factory.class.php
@@ -40,7 +40,7 @@ public static function get_logger_chain($interactive, $execution, $backupid) {
         global $CFG;
 
         $dfltloglevel = backup::LOG_WARNING; // Default logging level
-        if (debugging('', DEBUG_DEVELOPER)) { // Debug developer raises default logging level
+        if ($CFG->debugdeveloper) { // Debug developer raises default logging level
             $dfltloglevel = backup::LOG_DEBUG;
         }
 
diff --git a/backup/util/factories/tests/factories_test.php b/backup/util/factories/tests/factories_test.php
index 54dc4e99fd7f..2a3fa1a55eb6 100644
--- a/backup/util/factories/tests/factories_test.php
+++ b/backup/util/factories/tests/factories_test.php
@@ -94,7 +94,6 @@ function test_backup_factory() {
 
         // Instantiate with debugging enabled and $CFG->backup_error_log_logger_level not set
         $CFG->debugdisplay = true;
-        $CFG->debug = DEBUG_DEVELOPER;
         unset($CFG->backup_error_log_logger_level);
         $logger1 = backup_factory::get_logger_chain(backup::INTERACTIVE_YES, backup::EXECUTION_INMEDIATE, 'test');
         $this->assertTrue($logger1 instanceof error_log_logger);  // 1st logger is error_log_logger
diff --git a/cache/tests/administration_helper_test.php b/cache/tests/administration_helper_test.php
index 6a1630d7c692..c30ae0c648eb 100644
--- a/cache/tests/administration_helper_test.php
+++ b/cache/tests/administration_helper_test.php
@@ -189,11 +189,8 @@ public function test_get_edit_store_form() {
      * Test the hash_key functionality.
      */
     public function test_hash_key() {
-        global $CFG;
-
-        $currentdebugging = $CFG->debug;
-
-        $CFG->debug = E_ALL;
+        $this->resetAfterTest();
+        set_debugging(DEBUG_ALL);
 
         // First with simplekeys
         $instance = cache_config_phpunittest::instance(true);
@@ -230,7 +227,5 @@ public function test_hash_key() {
 
         $result = cache_helper::hash_key('test/test', $definition);
         $this->assertEquals(sha1($definition->generate_single_key_prefix().'-test/test'), $result);
-
-        $CFG->debug = $currentdebugging;
     }
 }
diff --git a/enrol/ldap/cli/sync.php b/enrol/ldap/cli/sync.php
index e43b12c16654..c1bff98536a4 100644
--- a/enrol/ldap/cli/sync.php
+++ b/enrol/ldap/cli/sync.php
@@ -46,7 +46,7 @@
 require_once("$CFG->libdir/clilib.php");
 
 // Ensure errors are well explained.
-$CFG->debug = DEBUG_DEVELOPER;
+set_debugging(DEBUG_DEVELOPER, true);
 
 if (!enrol_is_enabled('ldap')) {
     cli_error(get_string('pluginnotenabled', 'enrol_ldap'), 2);
diff --git a/install.php b/install.php
index 7b5fa2396777..899ebd35e38d 100644
--- a/install.php
+++ b/install.php
@@ -181,6 +181,9 @@
 $CFG->running_installer    = true;
 $CFG->early_install_lang   = true;
 $CFG->ostype               = (stristr(PHP_OS, 'win') && !stristr(PHP_OS, 'darwin')) ? 'WINDOWS' : 'UNIX';
+$CFG->debug                = (E_ALL | E_STRICT);
+$CFG->debugdisplay         = true;
+$CFG->debugdeveloper       = true;
 
 // Require all needed libs
 require_once($CFG->libdir.'/setuplib.php');
diff --git a/lib/accesslib.php b/lib/accesslib.php
index 29276381d3bf..386588a29a97 100644
--- a/lib/accesslib.php
+++ b/lib/accesslib.php
@@ -3807,7 +3807,7 @@ function get_users_by_capability(context $context, $capability, $fields = '', $s
             $fields = 'u.*';
         }
     } else {
-        if (debugging('', DEBUG_DEVELOPER) && strpos($fields, 'u.*') === false && strpos($fields, 'u.id') === false) {
+        if ($CFG->debugdeveloper && strpos($fields, 'u.*') === false && strpos($fields, 'u.id') === false) {
             debugging('u.id must be included in the list of fields passed to get_users_by_capability().', DEBUG_DEVELOPER);
         }
     }
diff --git a/lib/adminlib.php b/lib/adminlib.php
index 25ae3d0cae10..5d209bda3a2d 100644
--- a/lib/adminlib.php
+++ b/lib/adminlib.php
@@ -968,6 +968,8 @@ public function prune($name) {
      * @return bool True if successfully added, false if $something can not be added.
      */
     public function add($parentname, $something, $beforesibling = null) {
+        global $CFG;
+
         $parent = $this->locate($parentname);
         if (is_null($parent)) {
             debugging('parent does not exist!');
@@ -979,7 +981,7 @@ public function add($parentname, $something, $beforesibling = null) {
                 debugging('error - parts of tree can be inserted only into parentable parts');
                 return false;
             }
-            if (debugging('', DEBUG_DEVELOPER) && !is_null($this->locate($something->name))) {
+            if ($CFG->debugdeveloper && !is_null($this->locate($something->name))) {
                 // The name of the node is already used, simply warn the developer that this should not happen.
                 // It is intentional to check for the debug level before performing the check.
                 debugging('Duplicate admin page name: ' . $something->name, DEBUG_DEVELOPER);
diff --git a/lib/classes/component.php b/lib/classes/component.php
index 3f682218022c..0fa7c30d5feb 100644
--- a/lib/classes/component.php
+++ b/lib/classes/component.php
@@ -195,12 +195,9 @@ protected static function init() {
     protected static function is_developer() {
         global $CFG;
 
+        // Note we can not rely on $CFG->debug here because DB is not initialised yet.
         if (isset($CFG->config_php_settings['debug'])) {
-            // Standard moodle script.
             $debug = (int)$CFG->config_php_settings['debug'];
-        } else if (isset($CFG->debug)) {
-            // Usually script with ABORT_AFTER_CONFIG.
-            $debug = (int)$CFG->debug;
         } else {
             return false;
         }
diff --git a/lib/classes/event/base.php b/lib/classes/event/base.php
index 5fcd4047def8..f520fdd4e865 100644
--- a/lib/classes/event/base.php
+++ b/lib/classes/event/base.php
@@ -108,7 +108,7 @@ private final function __construct() {
      * @throws \coding_exception
      */
     public static final function create(array $data = null) {
-        global $PAGE, $USER;
+        global $PAGE, $USER, $CFG;
 
         $data = (array)$data;
 
@@ -178,7 +178,7 @@ public static final function create(array $data = null) {
         }
 
         // Warn developers if they do something wrong.
-        if (debugging('', DEBUG_DEVELOPER)) { // This should be replaced by new $CFG->slowdebug flag if introduced.
+        if ($CFG->debugdeveloper) {
             static $automatickeys = array('eventname', 'component', 'action', 'target', 'contextlevel', 'contextinstanceid', 'timecreated');
             static $initkeys = array('crud', 'level', 'objecttable');
 
@@ -187,10 +187,10 @@ public static final function create(array $data = null) {
                     continue;
 
                 } else if (in_array($key, $automatickeys)) {
-                    debugging("Data key '$key' is not allowed in \\core\\event\\base::create() method, it is set automatically");
+                    debugging("Data key '$key' is not allowed in \\core\\event\\base::create() method, it is set automatically", DEBUG_DEVELOPER);
 
                 } else if (in_array($key, $initkeys)) {
-                    debugging("Data key '$key' is not allowed in \\core\\event\\base::create() method, you need to set it in init() method");
+                    debugging("Data key '$key' is not allowed in \\core\\event\\base::create() method, you need to set it in init() method", DEBUG_DEVELOPER);
 
                 } else if (!in_array($key, self::$fields)) {
                     debugging("Data key '$key' does not exist in \\core\\event\\base");
@@ -395,7 +395,7 @@ protected function get_legacy_logdata() {
      * @throws \coding_exception
      */
     protected final function validate_before_trigger() {
-        global $DB;
+        global $DB, $CFG;
 
         if (empty($this->data['crud'])) {
             throw new \coding_exception('crud must be specified in init() method of each method');
@@ -407,38 +407,38 @@ protected final function validate_before_trigger() {
             throw new \coding_exception('objecttable must be specified in init() method if objectid present');
         }
 
-        if (debugging('', DEBUG_DEVELOPER)) { // This should be replaced by new $CFG->slowdebug flag if introduced.
+        if ($CFG->debugdeveloper) {
             // Ideally these should be coding exceptions, but we need to skip these for performance reasons
             // on production servers.
 
             if (!in_array($this->data['crud'], array('c', 'r', 'u', 'd'), true)) {
-                debugging("Invalid event crud value specified.");
+                debugging("Invalid event crud value specified.", DEBUG_DEVELOPER);
             }
             if (!is_number($this->data['level'])) {
-                debugging('Event property level must be a number');
+                debugging('Event property level must be a number', DEBUG_DEVELOPER);
             }
             if (self::$fields !== array_keys($this->data)) {
-                debugging('Number of event data fields must not be changed in event classes');
+                debugging('Number of event data fields must not be changed in event classes', DEBUG_DEVELOPER);
             }
             $encoded = json_encode($this->data['other']);
             if ($encoded === false or $this->data['other'] !== json_decode($encoded, true)) {
-                debugging('other event data must be compatible with json encoding');
+                debugging('other event data must be compatible with json encoding', DEBUG_DEVELOPER);
             }
             if ($this->data['userid'] and !is_number($this->data['userid'])) {
-                debugging('Event property userid must be a number');
+                debugging('Event property userid must be a number', DEBUG_DEVELOPER);
             }
             if ($this->data['courseid'] and !is_number($this->data['courseid'])) {
-                debugging('Event property courseid must be a number');
+                debugging('Event property courseid must be a number', DEBUG_DEVELOPER);
             }
             if ($this->data['objectid'] and !is_number($this->data['objectid'])) {
-                debugging('Event property objectid must be a number');
+                debugging('Event property objectid must be a number', DEBUG_DEVELOPER);
             }
             if ($this->data['relateduserid'] and !is_number($this->data['relateduserid'])) {
-                debugging('Event property relateduserid must be a number');
+                debugging('Event property relateduserid must be a number', DEBUG_DEVELOPER);
             }
             if ($this->data['objecttable']) {
                 if (!$DB->get_manager()->table_exists($this->data['objecttable'])) {
-                    debugging('Unknown table specified in objecttable field');
+                    debugging('Unknown table specified in objecttable field', DEBUG_DEVELOPER);
                 }
             }
         }
@@ -521,7 +521,7 @@ public final function is_restored() {
      * @throws \coding_exception if used after ::trigger()
      */
     public final function add_record_snapshot($tablename, $record) {
-        global $DB;
+        global $DB, $CFG;
 
         if ($this->triggered) {
             throw new \coding_exception('It is not possible to add snapshots after triggering of events');
@@ -529,9 +529,9 @@ public final function add_record_snapshot($tablename, $record) {
 
         // NOTE: this might use some kind of MUC cache,
         //       hopefully we will not run out of memory here...
-        if (debugging('', DEBUG_DEVELOPER)) { // This should be replaced by new $CFG->slowdebug flag if introduced.
+        if ($CFG->debugdeveloper) {
             if (!$DB->get_manager()->table_exists($tablename)) {
-                debugging("Invalid table name '$tablename' specified, database table does not exist.");
+                debugging("Invalid table name '$tablename' specified, database table does not exist.", DEBUG_DEVELOPER);
             }
         }
         $this->recordsnapshots[$tablename][$record->id] = $record;
diff --git a/lib/cronlib.php b/lib/cronlib.php
index 0bc2f0cebd5d..41c7bb2c604c 100644
--- a/lib/cronlib.php
+++ b/lib/cronlib.php
@@ -46,8 +46,7 @@ function cron_run() {
         $DB->set_debug(true);
     }
     if (!empty($CFG->showcrondebugging)) {
-        $CFG->debug = DEBUG_DEVELOPER;
-        $CFG->debugdisplay = true;
+        set_debugging(DEBUG_DEVELOPER, true);
     }
 
     set_time_limit(0);
diff --git a/lib/dml/pdo_moodle_database.php b/lib/dml/pdo_moodle_database.php
index cc7b3bb0e43d..58874bd016ba 100644
--- a/lib/dml/pdo_moodle_database.php
+++ b/lib/dml/pdo_moodle_database.php
@@ -308,16 +308,17 @@ public function get_fieldset_sql($sql, array $params=null) {
      * @return array of objects, or empty array if no records were found, or false if an error occurred.
      */
     public function get_records_sql($sql, array $params=null, $limitfrom=0, $limitnum=0) {
+        global $CFG;
+
         $rs = $this->get_recordset_sql($sql, $params, $limitfrom, $limitnum);
         if (!$rs->valid()) {
             $rs->close(); // Not going to iterate (but exit), close rs
             return false;
         }
         $objects = array();
-        $debugging = debugging('', DEBUG_DEVELOPER);
         foreach($rs as $value) {
             $key = reset($value);
-            if ($debugging && array_key_exists($key, $objects)) {
+            if ($CFG->debugdeveloper && array_key_exists($key, $objects)) {
                 debugging("Did you remember to make the first column something unique in your call to get_records? Duplicate value '$key' found in column first column of '$sql'.", DEBUG_DEVELOPER);
             }
             $objects[$key] = (object)$value;
diff --git a/lib/dml/tests/dml_test.php b/lib/dml/tests/dml_test.php
index 59b76019ca0e..07ee27e7d751 100644
--- a/lib/dml/tests/dml_test.php
+++ b/lib/dml/tests/dml_test.php
@@ -1475,8 +1475,6 @@ public function test_get_records_list() {
     }
 
     public function test_get_records_sql() {
-        global $CFG;
-
         $DB = $this->tdb;
         $dbman = $DB->get_manager();
 
@@ -1518,11 +1516,11 @@ public function test_get_records_sql() {
         $records = $DB->get_records_sql("SELECT course AS id, course AS course FROM {{$tablename}}", null);
         $this->assertDebuggingCalled();
         $this->assertEquals(6, count($records));
-        $CFG->debug = DEBUG_MINIMAL;
+        set_debugging(DEBUG_MINIMAL);
         $records = $DB->get_records_sql("SELECT course AS id, course AS course FROM {{$tablename}}", null);
         $this->assertDebuggingNotCalled();
         $this->assertEquals(6, count($records));
-        $CFG->debug = DEBUG_DEVELOPER;
+        set_debugging(DEBUG_DEVELOPER);
 
         // negative limits = no limits
         $records = $DB->get_records_sql("SELECT * FROM {{$tablename}} ORDER BY id", null, -1, -1);
@@ -1734,8 +1732,6 @@ public function test_get_record_select() {
     }
 
     public function test_get_record_sql() {
-        global $CFG;
-
         $DB = $this->tdb;
         $dbman = $DB->get_manager();
 
@@ -1774,10 +1770,10 @@ public function test_get_record_sql() {
 
         $this->assertNotEmpty($DB->get_record_sql("SELECT * FROM {{$tablename}}", array(), IGNORE_MISSING));
         $this->assertDebuggingCalled();
-        $CFG->debug = DEBUG_MINIMAL;
+        set_debugging(DEBUG_MINIMAL);
         $this->assertNotEmpty($DB->get_record_sql("SELECT * FROM {{$tablename}}", array(), IGNORE_MISSING));
         $this->assertDebuggingNotCalled();
-        $CFG->debug = DEBUG_DEVELOPER;
+        set_debugging(DEBUG_DEVELOPER);
 
         // multiple matches ignored
         $this->assertNotEmpty($DB->get_record_sql("SELECT * FROM {{$tablename}}", array(), IGNORE_MULTIPLE));
diff --git a/lib/editor/tinymce/classes/plugin.php b/lib/editor/tinymce/classes/plugin.php
index ed33fa49efc0..de303006de45 100644
--- a/lib/editor/tinymce/classes/plugin.php
+++ b/lib/editor/tinymce/classes/plugin.php
@@ -360,7 +360,7 @@ public function get_tinymce_file_url($file='', $absolute=true) {
         // Version number comes from plugin version.php, except in developer
         // mode where the special string 'dev' is used (prevents cacheing and
         // serves unminified JS).
-        if (debugging('', DEBUG_DEVELOPER)) {
+        if ($CFG->debugdeveloper) {
             $version = '-1';
         } else {
             $version = $this->get_version();
diff --git a/lib/editor/tinymce/cli/update_lang_files.php b/lib/editor/tinymce/cli/update_lang_files.php
index 790d42e44f95..1d692229a634 100644
--- a/lib/editor/tinymce/cli/update_lang_files.php
+++ b/lib/editor/tinymce/cli/update_lang_files.php
@@ -26,7 +26,7 @@
 
 require __DIR__ . '/../../../../config.php';
 
-if (!debugging('', DEBUG_DEVELOPER)) {
+if (!$CFG->debugdeveloper) {
     die('Only for developers!!!!!');
 }
 
diff --git a/lib/editor/tinymce/lib.php b/lib/editor/tinymce/lib.php
index eae4a60dd5a6..838f845dcddc 100644
--- a/lib/editor/tinymce/lib.php
+++ b/lib/editor/tinymce/lib.php
@@ -100,7 +100,7 @@ public function head_setup() {
     public function use_editor($elementid, array $options=null, $fpoptions=null) {
         global $PAGE, $CFG;
         // Note: use full moodle_url instance to prevent standard JS loader, make sure we are using https on profile page if required.
-        if (debugging('', DEBUG_DEVELOPER)) {
+        if ($CFG->debugdeveloper) {
             $PAGE->requires->js(new moodle_url($CFG->httpswwwroot.'/lib/editor/tinymce/tiny_mce/'.$this->version.'/tiny_mce_src.js'));
         } else {
             $PAGE->requires->js(new moodle_url($CFG->httpswwwroot.'/lib/editor/tinymce/tiny_mce/'.$this->version.'/tiny_mce.js'));
diff --git a/lib/filestorage/file_storage.php b/lib/filestorage/file_storage.php
index 9eeca4aab7b4..3783eeeba521 100644
--- a/lib/filestorage/file_storage.php
+++ b/lib/filestorage/file_storage.php
@@ -1624,6 +1624,8 @@ public function convert_image($filerecord, $fid, $newwidth = null, $newheight =
      * @return array (contenthash, filesize, newfile)
      */
     public function add_file_to_pool($pathname, $contenthash = NULL) {
+        global $CFG;
+
         if (!is_readable($pathname)) {
             throw new file_exception('storedfilecannotread', '', $pathname);
         }
@@ -1635,14 +1637,14 @@ public function add_file_to_pool($pathname, $contenthash = NULL) {
 
         if (is_null($contenthash)) {
             $contenthash = sha1_file($pathname);
-        } else if (debugging('', DEBUG_DEVELOPER)) {
+        } else if ($CFG->debugdeveloper) {
             $filehash = sha1_file($pathname);
             if ($filehash === false) {
                 throw new file_exception('storedfilecannotread', '', $pathname);
             }
             if ($filehash !== $contenthash) {
                 // Hopefully this never happens, if yes we need to fix calling code.
-                debugging("Invalid contenthash submitted for file $pathname");
+                debugging("Invalid contenthash submitted for file $pathname", DEBUG_DEVELOPER);
                 $contenthash = $filehash;
             }
         }
diff --git a/lib/formslib.php b/lib/formslib.php
index 075bd8039198..abeb09d1b468 100644
--- a/lib/formslib.php
+++ b/lib/formslib.php
@@ -61,7 +61,7 @@ function pear_handle_error($error){
     print_object($error->backtrace);
 }
 
-if (!empty($CFG->debug) and ($CFG->debug >= DEBUG_ALL or $CFG->debug == -1)){
+if ($CFG->debugdeveloper) {
     //TODO: this is a wrong place to init PEAR!
     $GLOBALS['_PEAR_default_error_mode'] = PEAR_ERROR_CALLBACK;
     $GLOBALS['_PEAR_default_error_options'] = 'pear_handle_error';
@@ -1261,7 +1261,9 @@ public static function get_js_module() {
      * @return void
      */
     private function detectMissingSetType() {
-        if (!debugging('', DEBUG_DEVELOPER)) {
+        global $CFG;
+
+        if (!$CFG->debugdeveloper) {
             // Only for devs.
             return;
         }
diff --git a/lib/installlib.php b/lib/installlib.php
index 461f552ff849..f60605b1eef5 100644
--- a/lib/installlib.php
+++ b/lib/installlib.php
@@ -424,6 +424,7 @@ function install_cli_database(array $options, $interactive) {
     @ini_set('display_errors', '1');
     $CFG->debug = (E_ALL | E_STRICT);
     $CFG->debugdisplay = true;
+    $CFG->debugdeveloper = true;
 
     $CFG->version = '';
     $CFG->release = '';
diff --git a/lib/minify/config.php b/lib/minify/config.php
index bf8fc20c9bf9..0750f229ae9a 100644
--- a/lib/minify/config.php
+++ b/lib/minify/config.php
@@ -14,7 +14,7 @@
 
 $min_enableBuilder = false;
 $min_errorLogger = false;
-$min_allowDebugFlag = debugging('', DEBUG_DEVELOPER);
+$min_allowDebugFlag = $CFG->debugdeveloper;
 $min_cachePath = $CFG->tempdir;
 $min_documentRoot = $CFG->dirroot.'/lib/minify';
 $min_cacheFileLocking = empty($CFG->preventfilelocking);
diff --git a/lib/moodlelib.php b/lib/moodlelib.php
index cfab5d8cbe1c..f32215c0cbbe 100644
--- a/lib/moodlelib.php
+++ b/lib/moodlelib.php
@@ -6728,8 +6728,8 @@ function get_string($identifier, $component = '', $a = null, $lazyload = false)
         return new lang_string($identifier, $component, $a);
     }
 
-    if (debugging('', DEBUG_DEVELOPER) && clean_param($identifier, PARAM_STRINGID) === '') {
-        throw new coding_exception('Invalid string identifier. The identifier cannot be empty. Please fix your get_string() call.');
+    if ($CFG->debugdeveloper && clean_param($identifier, PARAM_STRINGID) === '') {
+        throw new coding_exception('Invalid string identifier. The identifier cannot be empty. Please fix your get_string() call.', DEBUG_DEVELOPER);
     }
 
     // There is now a forth argument again, this time it is a boolean however so
@@ -7222,7 +7222,7 @@ function get_list_of_plugins($directory='mod', $exclude='', $basedir='') {
         $basedir = $basedir .'/'. $directory;
     }
 
-    if (empty($exclude) and debugging('', DEBUG_DEVELOPER)) {
+    if ($CFG->debugdeveloper and empty($exclude)) {
         // Make sure devs do not use this to list normal plugins,
         // this is intended for general directories that are not plugins!
 
@@ -10068,8 +10068,8 @@ protected function get_string() {
         // Check if we need to process the string.
         if ($this->string === null) {
             // Check the quality of the identifier.
-            if (debugging('', DEBUG_DEVELOPER) && clean_param($this->identifier, PARAM_STRINGID) === '') {
-                throw new coding_exception('Invalid string identifier. Most probably some illegal character is part of the string identifier. Please check your string definition');
+            if ($CFG->debugdeveloper && clean_param($this->identifier, PARAM_STRINGID) === '') {
+                throw new coding_exception('Invalid string identifier. Most probably some illegal character is part of the string identifier. Please check your string definition', DEBUG_DEVELOPER);
             }
 
             // Process the string.
diff --git a/lib/outputlib.php b/lib/outputlib.php
index 08da9d89ea35..be02e35db1e5 100644
--- a/lib/outputlib.php
+++ b/lib/outputlib.php
@@ -1678,7 +1678,8 @@ class xhtml_container_stack {
      * Constructor
      */
     public function __construct() {
-        $this->isdebugging = debugging('', DEBUG_DEVELOPER);
+        global $CFG;
+        $this->isdebugging = $CFG->debugdeveloper;
     }
 
     /**
diff --git a/lib/outputrenderers.php b/lib/outputrenderers.php
index be2dfea5836c..d61279a473b7 100644
--- a/lib/outputrenderers.php
+++ b/lib/outputrenderers.php
@@ -2532,7 +2532,7 @@ public function fatal_error($message, $moreinfourl, $link, $backtrace, $debuginf
         }
         $output .= $this->box($message, 'errorbox', null, array('data-rel' => 'fatalerror'));
 
-        if (debugging('', DEBUG_DEVELOPER)) {
+        if ($CFG->debugdeveloper) {
             if (!empty($debuginfo)) {
                 $debuginfo = s($debuginfo); // removes all nasty JS
                 $debuginfo = str_replace("\n", '<br />', $debuginfo); // keep newlines
@@ -3364,7 +3364,7 @@ public function heading($text, $level = 2, $classes = 'main', $id = null) {
     public function fatal_error($message, $moreinfourl, $link, $backtrace, $debuginfo = null) {
         $output = "!!! $message !!!\n";
 
-        if (debugging('', DEBUG_DEVELOPER)) {
+        if ($CFG->debugdeveloper) {
             if (!empty($debuginfo)) {
                 $output .= $this->notification($debuginfo, 'notifytiny');
             }
diff --git a/lib/outputrequirementslib.php b/lib/outputrequirementslib.php
index 4374c77a0585..ac06df994349 100644
--- a/lib/outputrequirementslib.php
+++ b/lib/outputrequirementslib.php
@@ -224,7 +224,7 @@ public function __construct() {
         ));
 
         // Set some more loader options applying to groups too.
-        if (debugging('', DEBUG_DEVELOPER)) {
+        if ($CFG->debugdeveloper) {
             // When debugging is enabled, we want to load the non-minified (RAW) versions of YUI library modules rather
             // than the DEBUG versions as these generally generate too much logging for our purposes.
             // However we do want the DEBUG versions of our Moodle-specific modules.
@@ -270,7 +270,7 @@ protected function init_requirements_data(moodle_page $page, core_renderer $rend
             'jsrev'               => ((empty($CFG->cachejs) or empty($CFG->jsrev)) ? -1 : $CFG->jsrev),
             'svgicons'            => $page->theme->use_svg_icons()
         );
-        if (debugging('', DEBUG_DEVELOPER)) {
+        if ($CFG->debugdeveloper) {
             $this->M_cfg['developerdebug'] = true;
         }
 
@@ -436,7 +436,7 @@ public function jquery_plugin($plugin, $component = 'core') {
         $this->jqueryplugins[$plugin]->urls      = array();
 
         foreach ($plugins[$plugin]['files'] as $file) {
-            if (debugging('', DEBUG_DEVELOPER)) {
+            if ($CFG->debugdeveloper) {
                 if (!file_exists("$componentdir/jquery/$file")) {
                     debugging("Invalid file '$file' specified in jQuery plugin '$plugin' in component '$component'");
                     continue;
@@ -746,7 +746,7 @@ public function js_module($module) {
 
         // Don't load this module if we already have, no need to!
         if ($this->js_module_loaded($module['name'])) {
-            if (debugging('', DEBUG_DEVELOPER)) {
+            if ($CFG->debugdeveloper) {
                 $this->debug_moduleloadstacktraces[$module['name']][] = format_backtrace(debug_backtrace());
             }
             return;
@@ -780,7 +780,7 @@ public function js_module($module) {
         } else {
             $this->YUI_config->add_module_config($module['name'], $module);
         }
-        if (debugging('', DEBUG_DEVELOPER)) {
+        if ($CFG->debugdeveloper) {
             if (!array_key_exists($module['name'], $this->debug_moduleloadstacktraces)) {
                 $this->debug_moduleloadstacktraces[$module['name']] = array();
             }
diff --git a/lib/phpunit/bootstrap.php b/lib/phpunit/bootstrap.php
index 6dee6211041c..749bcfa8b731 100644
--- a/lib/phpunit/bootstrap.php
+++ b/lib/phpunit/bootstrap.php
@@ -198,6 +198,7 @@
 
 // force the same CFG settings in all sites
 $CFG->debug = (E_ALL | E_STRICT); // can not use DEBUG_DEVELOPER yet
+$CFG->debugdeveloper = true;
 $CFG->debugdisplay = 1;
 error_reporting($CFG->debug);
 ini_set('display_errors', '1');
diff --git a/lib/phpunit/classes/advanced_testcase.php b/lib/phpunit/classes/advanced_testcase.php
index 0a4848d9141f..1bd0d7d891fe 100644
--- a/lib/phpunit/classes/advanced_testcase.php
+++ b/lib/phpunit/classes/advanced_testcase.php
@@ -248,7 +248,8 @@ public function getDebuggingMessages() {
     }
 
     /**
-     * Clear all previous debugging messages in current test.
+     * Clear all previous debugging messages in current test
+     * and revert to default DEVELOPER_DEBUG level.
      */
     public function resetDebugging() {
         phpunit_util::reset_debugging();
diff --git a/lib/phpunit/classes/util.php b/lib/phpunit/classes/util.php
index 552e78aaca8b..4b9d7a046580 100644
--- a/lib/phpunit/classes/util.php
+++ b/lib/phpunit/classes/util.php
@@ -594,6 +594,7 @@ public static function debugging_triggered($message, $level, $from) {
      */
     public static function reset_debugging() {
         self::$debuggings = array();
+        set_debugging(DEBUG_DEVELOPER);
     }
 
     /**
diff --git a/lib/phpunit/tests/advanced_test.php b/lib/phpunit/tests/advanced_test.php
index 61f5a30f951a..f6c071908c9f 100644
--- a/lib/phpunit/tests/advanced_test.php
+++ b/lib/phpunit/tests/advanced_test.php
@@ -65,9 +65,10 @@ public function test_debugging() {
         $debuggings = $this->getDebuggingMessages();
         $this->assertEquals(0, count($debuggings));
 
-        $CFG->debug = DEBUG_NONE;
+        set_debugging(DEBUG_NONE);
         debugging('hokus');
         $this->assertDebuggingNotCalled();
+        set_debugging(DEBUG_DEVELOPER);
     }
 
     public function test_set_user() {
diff --git a/lib/setup.php b/lib/setup.php
index acc466adfc91..f0ba4a5561f0 100644
--- a/lib/setup.php
+++ b/lib/setup.php
@@ -143,6 +143,11 @@
     }
 }
 
+// Make sure there is some database table prefix.
+if (!isset($CFG->prefix)) {
+    $CFG->prefix = '';
+}
+
 // Define admin directory
 if (!isset($CFG->admin)) {   // Just in case it isn't defined in config.php
     $CFG->admin = 'admin';   // This is relative to the wwwroot and dirroot
@@ -166,6 +171,16 @@
     $CFG->localcachedir = "$CFG->dataroot/localcache";
 }
 
+// Location of all languages except core English pack.
+if (!isset($CFG->langotherroot)) {
+    $CFG->langotherroot = $CFG->dataroot.'/lang';
+}
+
+// Location of local lang pack customisations (dirs with _local suffix).
+if (!isset($CFG->langlocalroot)) {
+    $CFG->langlocalroot = $CFG->dataroot.'/lang';
+}
+
 // The current directory in PHP version 4.3.0 and above isn't necessarily the
 // directory of the script when run from the command line. The require_once()
 // would fail, so we'll have to chdir()
@@ -309,6 +324,23 @@
 $CFG->yui2version = '2.9.0';
 $CFG->yui3version = '3.9.1';
 
+// Store settings from config.php in array in $CFG - we can use it later to detect problems and overrides.
+if (!isset($CFG->config_php_settings)) {
+    $CFG->config_php_settings = (array)$CFG;
+    // Forced plugin settings override values from config_plugins table.
+    unset($CFG->config_php_settings['forced_plugin_settings']);
+    if (!isset($CFG->forced_plugin_settings)) {
+        $CFG->forced_plugin_settings = array();
+    }
+}
+
+if (isset($CFG->debug)) {
+    $CFG->debug = (int)$CFG->debug;
+} else {
+    $CFG->debug = 0;
+}
+$CFG->debugdeveloper = ($CFG->debug & E_ALL and $CFG->debug & E_STRICT); // DEBUG_DEVELOPER is not available yet.
+
 if (!defined('MOODLE_INTERNAL')) { // Necessary because cli installer has to define it earlier.
     /** Used by library scripts to check they are being called by Moodle. */
     define('MOODLE_INTERNAL', true);
@@ -321,11 +353,7 @@
 if (defined('ABORT_AFTER_CONFIG')) {
     if (!defined('ABORT_AFTER_CONFIG_CANCEL')) {
         // hide debugging if not enabled in config.php - we do not want to disclose sensitive info
-        if (isset($CFG->debug)) {
-            error_reporting($CFG->debug);
-        } else {
-            error_reporting(0);
-        }
+        error_reporting($CFG->debug);
         if (NO_DEBUG_DISPLAY) {
             // Some parts of Moodle cannot display errors and debug at all.
             ini_set('display_errors', '0');
@@ -454,13 +482,6 @@
  */
 global $SCRIPT;
 
-// Store settings from config.php in array in $CFG - we can use it later to detect problems and overrides
-$CFG->config_php_settings = (array)$CFG;
-// Forced plugin settings override values from config_plugins table
-unset($CFG->config_php_settings['forced_plugin_settings']);
-if (!isset($CFG->forced_plugin_settings)) {
-    $CFG->forced_plugin_settings = array();
-}
 // Set httpswwwroot default value (this variable will replace $CFG->wwwroot
 // inside some URLs used in HTTPSPAGEREQUIRED pages.
 $CFG->httpswwwroot = $CFG->wwwroot;
@@ -505,20 +526,6 @@
     exit(1);
 }
 
-if (!isset($CFG->prefix)) {   // Just in case it isn't defined in config.php
-    $CFG->prefix = '';
-}
-
-// location of all languages except core English pack
-if (!isset($CFG->langotherroot)) {
-    $CFG->langotherroot = $CFG->dataroot.'/lang';
-}
-
-// location of local lang pack customisations (dirs with _local suffix)
-if (!isset($CFG->langlocalroot)) {
-    $CFG->langlocalroot = $CFG->dataroot.'/lang';
-}
-
 //point pear include path to moodles lib/pear so that includes and requires will search there for files before anywhere else
 //the problem is that we need specific version of quickforms and hacked excel files :-(
 ini_set('include_path', $CFG->libdir.'/pear' . PATH_SEPARATOR . ini_get('include_path'));
@@ -579,20 +586,40 @@
     unset($dbhash);
 }
 
-// Disable errors for now - needed for installation when debug enabled in config.php
-if (isset($CFG->debug)) {
-    $originalconfigdebug = $CFG->debug;
-    unset($CFG->debug);
+// Load up any configuration from the config table or MUC cache.
+if (PHPUNIT_TEST) {
+    phpunit_util::initialise_cfg();
 } else {
-    $originalconfigdebug = null;
+    initialise_cfg();
 }
 
-// Load up any configuration from the config table
+if (isset($CFG->debug)) {
+    $CFG->debug = (int)$CFG->debug;
+    error_reporting($CFG->debug);
+}  else {
+    $CFG->debug = 0;
+}
+$CFG->debugdeveloper = ($CFG->debug & DEBUG_DEVELOPER);
 
-if (PHPUNIT_TEST) {
-    phpunit_util::initialise_cfg();
+// Find out if PHP configured to display warnings,
+// this is a security problem because some moodle scripts may
+// disclose sensitive information.
+if (ini_get_bool('display_errors')) {
+    define('WARN_DISPLAY_ERRORS_ENABLED', true);
+}
+// If we want to display Moodle errors, then try and set PHP errors to match.
+if (!isset($CFG->debugdisplay)) {
+    // Keep it "as is" during installation.
+} else if (NO_DEBUG_DISPLAY) {
+    // Some parts of Moodle cannot display errors and debug at all.
+    ini_set('display_errors', '0');
+    ini_set('log_errors', '1');
+} else if (empty($CFG->debugdisplay)) {
+    ini_set('display_errors', '0');
+    ini_set('log_errors', '1');
 } else {
-    initialise_cfg();
+    // This is very problematic in XHTML strict mode!
+    ini_set('display_errors', '1');
 }
 
 // Verify upgrade is not running unless we are in a script that needs to execute in any case
@@ -609,14 +636,6 @@
     $DB->set_logging(true);
 }
 
-// Prevent warnings from roles when upgrading with debug on
-if (isset($CFG->debug)) {
-    $originaldatabasedebug = $CFG->debug;
-    unset($CFG->debug);
-} else {
-    $originaldatabasedebug = null;
-}
-
 // enable circular reference collector in PHP 5.3,
 // it helps a lot when using large complex OOP structures such as in amos or gradebook
 if (function_exists('gc_enable')) {
@@ -628,40 +647,6 @@
     register_shutdown_function('moodle_request_shutdown');
 }
 
-// Set error reporting back to normal
-if ($originaldatabasedebug === null) {
-    $CFG->debug = DEBUG_MINIMAL;
-} else {
-    $CFG->debug = $originaldatabasedebug;
-}
-if ($originalconfigdebug !== null) {
-    $CFG->debug = $originalconfigdebug;
-}
-unset($originalconfigdebug);
-unset($originaldatabasedebug);
-error_reporting($CFG->debug);
-
-// find out if PHP configured to display warnings,
-// this is a security problem because some moodle scripts may
-// disclose sensitive information
-if (ini_get_bool('display_errors')) {
-    define('WARN_DISPLAY_ERRORS_ENABLED', true);
-}
-// If we want to display Moodle errors, then try and set PHP errors to match
-if (!isset($CFG->debugdisplay)) {
-    // keep it "as is" during installation
-} else if (NO_DEBUG_DISPLAY) {
-    // some parts of Moodle cannot display errors and debug at all.
-    ini_set('display_errors', '0');
-    ini_set('log_errors', '1');
-} else if (empty($CFG->debugdisplay)) {
-    ini_set('display_errors', '0');
-    ini_set('log_errors', '1');
-} else {
-    // This is very problematic in XHTML strict mode!
-    ini_set('display_errors', '1');
-}
-
 // detect unsupported upgrade jump as soon as possible - do not change anything, do not use system functions
 if (!empty($CFG->version) and $CFG->version < 2007101509) {
     print_error('upgraderequires19', 'error');
diff --git a/lib/setuplib.php b/lib/setuplib.php
index f75a8a9bd04c..1b43764f4498 100644
--- a/lib/setuplib.php
+++ b/lib/setuplib.php
@@ -729,25 +729,28 @@ function setup_validate_php_configuration() {
 }
 
 /**
- * Initialise global $CFG variable
- * @return void
+ * Initialise global $CFG variable.
+ * @private to be used only from lib/setup.php
  */
 function initialise_cfg() {
     global $CFG, $DB;
 
+    if (!$DB) {
+        // This should not happen.
+        return;
+    }
+
     try {
-        if ($DB) {
-            $localcfg = get_config('core');
-            foreach ($localcfg as $name => $value) {
-                if (property_exists($CFG, $name)) {
-                    // config.php settings always take precedence
-                    continue;
-                }
-                $CFG->{$name} = $value;
-            }
-        }
+        $localcfg = get_config('core');
     } catch (dml_exception $e) {
-        // most probably empty db, going to install soon
+        // Most probably empty db, going to install soon.
+        return;
+    }
+
+    foreach ($localcfg as $name => $value) {
+        // Note that get_config() keeps forced settings
+        // and normalises values to string if possible.
+        $CFG->{$name} = $value;
     }
 }
 
diff --git a/lib/tests/event_test.php b/lib/tests/event_test.php
index 414d105ff9b6..2c06a4306dea 100644
--- a/lib/tests/event_test.php
+++ b/lib/tests/event_test.php
@@ -637,10 +637,10 @@ public function test_problematic_events() {
         $event2 = \core_tests\event\problematic_event1::create(array('xxx'=>0, 'context'=>\context_system::instance()));
         $this->assertDebuggingCalled();
 
-        $CFG->debug = 0;
+        set_debugging(DEBUG_NONE);
         $event3 = \core_tests\event\problematic_event1::create(array('xxx'=>0, 'context'=>\context_system::instance()));
         $this->assertDebuggingNotCalled();
-        $CFG->debug = E_ALL | E_STRICT;
+        set_debugging(DEBUG_DEVELOPER);
 
         $event4 = \core_tests\event\problematic_event1::create(array('context'=>\context_system::instance(), 'other'=>array('a'=>1)));
         $event4->trigger();
diff --git a/lib/tests/statslib_test.php b/lib/tests/statslib_test.php
index fe9728caf060..50fd289d7f5e 100644
--- a/lib/tests/statslib_test.php
+++ b/lib/tests/statslib_test.php
@@ -299,24 +299,22 @@ protected function verify_stats($expected, $output = '') {
      * Test progress output when debug is on.
      */
     public function test_statslib_progress_debug() {
-        global $CFG;
-
-        $CFG->debug = DEBUG_ALL;
+        set_debugging(DEBUG_ALL);
         $this->expectOutputString('1:0 ');
         stats_progress('init');
         stats_progress('1');
+        $this->resetDebugging();
     }
 
     /**
      * Test progress output when debug is off.
      */
     public function test_statslib_progress_no_debug() {
-        global $CFG;
-
-        $CFG->debug = DEBUG_NONE;
+        set_debugging(DEBUG_NONE);
         $this->expectOutputString('.');
         stats_progress('init');
         stats_progress('1');
+        $this->resetDebugging();
     }
 
     /**
diff --git a/lib/upgrade.txt b/lib/upgrade.txt
index f7fc350bebba..29a297f941f7 100644
--- a/lib/upgrade.txt
+++ b/lib/upgrade.txt
@@ -16,6 +16,8 @@ information provided here is intended especially for developers.
 * The string manager classes were renamed. Note that they should not be modified or used directly,
   always use get_string_manager() to get instance of the string manager.
 * The ability to use an 'insecure' rc4encrypt/rc4decrypt key has been removed.
+* Use $CFG->debugdeveloper instead of debugging('', DEBUG_DEVELOPER).
+* Use set_debugging(DEBUG_xxx) when changing debugging level for current request.
 
 DEPRECATIONS:
 Various previously deprecated functions have now been altered to throw DEBUG_DEVELOPER debugging notices
diff --git a/lib/upgradelib.php b/lib/upgradelib.php
index e49b9568f5fd..3edf94dc598a 100644
--- a/lib/upgradelib.php
+++ b/lib/upgradelib.php
@@ -1148,7 +1148,7 @@ function upgrade_handle_exception($ex, $plugin = null) {
     upgrade_log(UPGRADE_LOG_ERROR, $plugin, 'Exception: ' . get_class($ex), $info->message, $info->backtrace);
 
     // Always turn on debugging - admins need to know what is going on
-    $CFG->debug = DEBUG_DEVELOPER;
+    set_debugging(DEBUG_DEVELOPER, true);
 
     default_exception_handler($ex, true, $plugin);
 }
diff --git a/lib/weblib.php b/lib/weblib.php
index ee1d160bdd44..2b6c7d7f9817 100644
--- a/lib/weblib.php
+++ b/lib/weblib.php
@@ -1216,7 +1216,7 @@ function format_text($text, $format = FORMAT_MOODLE, $options = null, $courseidd
         // the text before storing into database which would be itself big bug..
         $text = str_replace("\"$CFG->httpswwwroot/draftfile.php", "\"$CFG->httpswwwroot/brokenfile.php#", $text);
 
-        if (debugging('', DEBUG_DEVELOPER)) {
+        if ($CFG->debugdeveloper) {
             if (strpos($text, '@@PLUGINFILE@@/') !== false) {
                 debugging('Before calling format_text(), the content must be processed with file_rewrite_pluginfile_urls()',
                     DEBUG_DEVELOPER);
@@ -2791,6 +2791,24 @@ function print_tabs($tabrows, $selected = null, $inactive = null, $activated = n
     }
 }
 
+/**
+ * Alter debugging level for the current request,
+ * the change is not saved in database.
+ *
+ * @param int $level one of the DEBUG_* constants
+ * @param bool $debugdisplay
+ */
+function set_debugging($level, $debugdisplay = null) {
+    global $CFG;
+
+    $CFG->debug = (int)$level;
+    $CFG->debugdeveloper = ($CFG->debug & DEBUG_DEVELOPER);
+
+    if ($debugdisplay !== null) {
+        $CFG->debugdisplay = (bool)$debugdisplay;
+    }
+}
+
 /**
  * Standard Debugging Function
  *
diff --git a/mod/workshop/renderer.php b/mod/workshop/renderer.php
index a4311a8a5970..4a29a74b9f86 100644
--- a/mod/workshop/renderer.php
+++ b/mod/workshop/renderer.php
@@ -339,6 +339,7 @@ protected function render_workshop_user_plan(workshop_user_plan $plan) {
      * @return string HTML to be echoed
      */
     protected function render_workshop_allocation_result(workshop_allocation_result $result) {
+        global $CFG;
 
         $status = $result->get_status();
 
@@ -384,7 +385,7 @@ protected function render_workshop_allocation_result(workshop_allocation_result
         if (is_array($logs) and !empty($logs)) {
             $o .= html_writer::start_tag('ul', array('class' => 'allocation-init-results'));
             foreach ($logs as $log) {
-                if ($log->type == 'debug' and !debugging('', DEBUG_DEVELOPER)) {
+                if ($log->type == 'debug' and !$CFG->debugdeveloper) {
                     // display allocation debugging messages for developers only
                     continue;
                 }
diff --git a/report/performance/locallib.php b/report/performance/locallib.php
index b14a12756800..993054638bb4 100644
--- a/report/performance/locallib.php
+++ b/report/performance/locallib.php
@@ -209,13 +209,9 @@ public static function report_performance_check_debugmsg() {
                             DEBUG_NORMAL => 'debugnormal',
                             DEBUG_ALL => 'debugall',
                             DEBUG_DEVELOPER => 'debugdeveloper');
-        // If debug is not set then consider it as 0.
-        if (!isset($CFG->themedesignermode)) {
-            $CFG->debug = DEBUG_NONE;
-        }
 
         $issueresult->statusstr = get_string($debugchoices[$CFG->debug], 'admin');
-        if ($CFG->debug != DEBUG_DEVELOPER) {
+        if (!$CFG->debugdeveloper) {
             $issueresult->status = self::REPORT_PERFORMANCE_OK;
             $issueresult->comment = get_string('check_debugmsg_comment_nodeveloper', 'report_performance');
         } else {