fixes after @samdark review

framework/widgets/Pjax.php

@@ -98,10 +98,15 @@ class Pjax extends Widget
      */
     public $clientOptions;
     /**
-     * @var string the prefix to the automatically generated pjax widget IDs.
-     * @see getId()
+     * @inheritdoc
+     * Note: This variable must be redeclared to force separate counting for Pjax widgets (issue #12969)
+     */
+    public static $counter = 0;
+    /**
+     * @inheritdoc
      */
-    public static $pjaxAutoIdPrefix = 'w_pjax_';
+    public static $autoIdPrefix = 'p';
+
 
     /**
      * @inheritdoc
@@ -136,23 +141,6 @@ public function init()
         }
     }
 
-    /**
-     * Custom ID generation for Pjax widgets
-     * This override is to attain a more reliable match between ID's of local and remote Pjax widgets (#12969)
-     * The implementation follows the solution proposed in the following comment:
-     * @link https://github.com/yiisoft/yii2/pull/12977#issuecomment-260123078
-     * @since 2.0.11
-     */
-    private static $pjaxCounter = 0;
-    private $_pjaxId;
-    public function getId($autoGenerate = true)
-    {
-        if ($autoGenerate && $this->_pjaxId === null) {
-            $this->_pjaxId = static::$pjaxAutoIdPrefix . static::$pjaxCounter++;
-        }
-        return $this->_pjaxId;
-    }
-
     /**
      * @inheritdoc
      */

tests/framework/widgets/PjaxTest.php

@@ -22,8 +22,8 @@ public function testGeneratedIdByPjaxWidget()
 
         $this->assertEquals('w0', $nonPjaxWidget1->options['id']);
         $this->assertEquals('w1', $nonPjaxWidget2->options['id']);
-        $this->assertEquals('w_pjax_0', $pjax1->options['id']);
-        $this->assertEquals('w_pjax_1', $pjax2->options['id']);
+        $this->assertEquals('p0', $pjax1->options['id']);
+        $this->assertEquals('p1', $pjax2->options['id']);
     }
 
     protected function setUp()