Evert Pot has posted a handy tip for Firefox users when it comes to searching the PHP.net manual for a specific function - an addition to the Quicksearch.

If you're a PHP developer, you'll likely often need to open up php.net to find out the [the order of ;)] arguments for a function. Generally i just type, php.net/functionname, but if you want to save 4 more keystrokes you can easily add a quick search.

He's included a screenshot of the interface to add it as well as the location to give - a URL pointing to the search page on the php.net website that looks in the "quickref" category for a match.