PHP 5 supports exceptions, via try, catch and throw.

The default exception is the Exception class.

<?php
define('NUM', 10);
try {
    if (NUM < 20) {
        throw new Exception(
            NUM . " is too small!"
        );
    }
} catch (Exception $e) {
    echo $e->getMessage();
    echo "\n<br />\n";
}
?>
Output
10 is too small!