Since most answers here are unnecesarily verbose, here's my non-ugly version of the top voted answer:
function errorHandler($errno, $errstr, $errfile = '', $errline = 0, $errcontext = array()) {
//Do stuff: mail, log, etc
}
function fatalHandler() {
$error = error_get_last();
if($error) errorHandler($error["type"], $error["message"], $error["file"], $error["line"]);
}
set_error_handler("errorHandler")
register_shutdown_function("fatalHandler");