Check this website out!
It has many types of "cheat" sheets that can be very usufull in web development:
http://codebangers.com/?p=271

I especially like this one:
http://www.dreamincode.net/downloads/ref_sheets/php_reference_sheet.pdf
It is the more basic one for php, but it have the most used commands and can come very useful even to more advanced programmers.