I am planning to use MYSQL. Is there a connection pooling extension available? Or what is the normal practice for connection? Is this the one used in every where...
This is an old question, but I wanted to add my two cents, as I was looking at this same issue. As of PHP 5.3, mysqli supports persistent connections, you just need to prepend p: to the front of the host name.
If you are running Apache, have you tried looking into connection pooling with mysql through the Apache mod_dbd module? It supports connection pooling for MySQL. http://httpd.apache.org/docs/2.2/mod/mod_dbd.html