I have installed postgres9.4 and pgadmin3. After that i try to install "install pdo_pgsql" for php connection, but its giving error and not installing the package because of some dependency. And I am getting error message like this "Call to undefined function pg_pconnect()".
Can't you just:
yum install php-pgsql.x86_64
You'll need to restart httpd after. Ensure the module's loaded by checking the module list or:
echo phpinfo();