In che parte del file php.ini si può inserire l'estensione dinamica extension=mysql.so ?

Nel file ho trovato solo questa indicazione, ma non dove si deve attuare.

codice:
;;;;;;;;;;;;;;;;;;;;;;
; Dynamic Extensions ;
;;;;;;;;;;;;;;;;;;;;;;
;
; If you wish to have an extension loaded automatically, use the following
; syntax:
;
;   extension=modulename.extension
;
; For example:
;
;   extension=msql.so
;
; Note that it should be the name of the module only; no directory information 
; needs to go here.  Specify the location of the extension with the
; extension_dir directive above.


;;;;
; Note: packaged extension modules are now loaded via the .ini files
; found in the directory /etc/php.d; these are loaded by default.
;;;;