WAMP maintains a different php.ini for the Apache dir and the PHP dir.
The WAMP control panel maintains the PHP.INI in the apache dir
(for example C:\wamp2.4\bin\apache\Apache2.4.4\php.ini)
There is also another PHP.INI, using by the command-line PHP, in the PHP directory
(for example C:\wamp2.4\bin\php\php5.4.16\php.ini)
Edit the PHP.INI file in the PHP dir and uncomment the following line