This parameter is only the filename of the extension to load which also depends on your platform. For example, the sockets extension (if compiled as a shared module, not the default!) would be called sockets.so on Unix platforms whereas it is called php_sockets.dll on the Windows platform.

The directory where the extension is loaded from depends on your platform:

Windows - If not explicitly set in the php.ini , the extension is loaded from C:\php5\ by default.

Unix - If not explicitly set in the php.ini , the default extension directory depends on

whether PHP has been built with --enable-debug or not

whether PHP has been built with (experimental) ZTS (Zend Thread Safety) support or not

the current internal ZEND_MODULE_API_NO (Zend internal module API number, which is basically the date on which a major module API change happened, e.g. 20010901 )

<install-dir>/lib/php/extensions/ <debug-or-not>-<zts-or-not>-ZEND_MODULE_API_NO

/usr/local/php/lib/php/extensions/debug-non-zts-20010901

/usr/local/php/lib/php/extensions/no-debug-zts-20010901