You want to change the value of a PHP configuration setting.
Use ini_set( ):
// add a directory to the include path ini_set('include_path', ini_get('include_path') . ':/home/fezzik/php');
Configuration variables are not permanently changed by ini_set( ). The new value lasts only for the duration of the request in which ini_set( ) is called. To make a persistent modification, alter the values stored in the php.ini file.
It isn't meaningful to alter certain variables, such as asp_tags, because by the time you call ini_set( ) to modify the setting, it's too late to change the behavior the setting affects. If a variable can't be changed, ini_set( ) returns false.
However, it is useful to alter configuration variables in certain pages. For example, if you're running a script from the command line, set html_errors to off.
To reset a variable back to its original setting, use ini_restore( ):
ini_restore('sendmail_from'); // go back to the default value
20.5.4. See Also
Recipe 20.4 on getting values of configuration variables; documentation on ini_set( ) at http://www.php.net/ini-set and ini_restore( ) at http://www.php.net/ini-restore.