recently i install the Wamp last version in my local computer. Before that i used php in Windows 7 - IIS 7.5. I used PDO mysql and it workd just fine.
try {
If you get this error while you can still see it enabled in php.ini then WAMP is responsible for this issue.
I suggest you to use XAMPP instead.
Please check if you are editing on php.ini in the apache servers bin folder (e.g: \apache2.4.18\bin) If you are editing the php.ini in your php folder those changes will not work. Please check your php.ini in your apache\bin to see if you have extension=php_mysql.dll and don't forget to restart the services.