PHP source code
PHP is a scripting language, as is ASP. Both languages can dynamically modify the website pages that are displayed to the computer user.
For example, a bank statement can be displayed on a website to the user who has requested it.
Without a scripting language, the bank would need to prepare a bank statement page for each of their customers.
With a scripting language such as PHP, there would only need to be one single bank statement template with spaces for each bit of variable data, for example names, balances etc.
PHP can build the website page with all the variable data in the correct places and then display the web page to the user.
PHP Sourcecode - links to websites
www.opensourcescripts.com
www.sourceforge.net
www.freshmeat.net
pear.php.net
directory.fsf.org
codewiki.wikispaces.com
www.phpclasses.org
source: wikipedia