MongoDB PHP Driver installation

I am trying to add mongodb php driver . I have php version 5.5.12 and apache x64 . I enabled it in php.ini file (extension=php_mongo.dll) and downloaded the php_mongo.dll and placed in ext folder inside PHP and restart the apache server .But doesn't work. When i check in phpinfo() it doen't show about mongodb. I tried many time changing different version of mongodb driver but can't get the solution.Does anyone have the solution for this?? Thanks in advance.