I needed a way to manually install PHP 5.4, because there's no PHP 5.4 addon for my WampServer version.
This thread is a bit old but I'll give the procedure here, as it match to the original question.
I'll take PHP 5.4.13 for my example (currently the most recent 5.4 version)
wampserver.conffrom another php folder (like
php/php5.2.8/) to the new folder
note: if you are adding php version 5.6, you need to copy
php5apache2_4.dll from other php folder, too, otherwise the wamp server won't start.
I too needed to upgrade PHP in WAMP recently. There are a handful of steps to properly do so. I covered them all and provided screenshots in the post linked to above.
Hope it helps!
This is another helpful article about changing the php version in wamp.
A useful detail that is mentioned in the article is to update the environment variable to point to the new php, so you can get access to the right php cli.