where can i get php extension for postgresql?

Maybe from PHP? http://ar.php.net/pgsql

Acording to that documentation, you'll need to recompile php with support for postgresql. First install PostgreSQL and then recompile PHP with the option stated there.
To recompile PHP (if you're not used to compile stuff) grab all the files here (including the pear subdirectory): http://mirror.switch.ch/ftp/mirror/s.../source/n/php/
After you have them put it in a directory with a subdirectory pear with the files that should be there. Then edit php.SlackBuild file adding the option (there are options in that file, you'll know where to put it) and finally run it: sh php.SlackBuild
If all goes fine, it will recompile PHP and leave the new package under /tmp.

Or you can do what I did here, and save tons of valuable time

Thanks Azmeen and gbonhevi for your inputs on this one. I followed Azmeen's post and that did the trick for me although I was about to with gbonhevi's suggestion...Thanks for the tips.

Tux,