small fix to php.ini documentation

documentation/ini.html

@@ -50,7 +50,7 @@ <h1>Reading php.ini variables</h1>
 </p>
 <p>
     You can only retrieve <i>predefined</i> variables from the php.ini. It is thus not 
-    possible to call Php::ini_get() with random strings. If you want to define
+    possible to call Php::ini_get() with random strings. If you want to use
     your own variables, you must first register them in the get_module()
     function before you can call Php::ini_get() to retrieve the current values.
 </p>