Almost every function seems to have a quick usage on it. Plus it has a by order description of the language.
That assumes you have programming experience. If you do not, you need to instead learn how to write algorithms. Searching doesn't seem to be quite so easy on these ones; I can find plenty of algorithms, but they are more conceptual for solving existing problems (ie: graphing datastructures and pattern implementations) than on how to write them from scratch.
header('HTTP/1.1 420 Enhance Your Calm');