I'm not sure when this came out, but Google now has source code search. These guys never stop amazing me.
So what you need to do now is create a new bookmark in firefox. Point it to: http://www.google.com/codesearch?hl=en&q=+lang:php+%s
Give it a name and in the keyword field, put something like 'phpcode'. Save it.
Now in your address bar, type 'phpcode array_merge' and return.
You'll see a page full of source code snippets that use the array_merge() function. Quick reference next time you need some sample code.
Thanks for the info. Google source code search is something new to me. Now, I can use it to find php codes...