Any ideas for simple, always useful PHP functions?

A regular expression to check if an e-mail address is valid. Tons of examples out there but it gets your hands dirty with a few necessary techniques.

Great idea John, thanks :)

there is always the login and logout. making them into function would come handy and easy to use. Sorry I am blank too :S

This isn’t too useful but it can save a little typing

function isPost() {
return $_SERVER[‘REQUEST_METHOD’] == ‘POST’;
}

if (isPost()) {
/* do form stuff */
}