The CLI (command line interface) SAPI has been introduced
with a goal of making PHP better at supporting the creation of 
stand alone applications.

It is based on CGI SAPI with all CGI specific things removed.

The main differences between the two:

* CLI is started up in quiet mode by default.
  (-q switch kept for compatibility)
* It does not change the working directory to that of the script.
  (-C switch kept for compatibility)
* Plain text error message
* $argc and $argv registered irrespective of the register_argc_argv 
  php.ini setting.
* implicit_flush always on
* -r option which allows execution of PHP code directly from
  the command line (e.g. php -r 'echo md5("test");' )
* Other more sophisticated command line switches (see: man php)
* max_execution_time is set to unlimited, overriding php.ini setting.