Wampserver has a problem when loading php_pdo_pgsql and php_pgsql modules. After searching on several forums the solution is to download from http://www.bmedon.net/download.
You have to load libpq.dll that comes with php, in the httpd.conf like this:
libpq.dll
httpd.conf
LoadFile "c:/wamp/bin/php/php5.4.3/libpq.dll"
It worked for me