Exceptions.php

<?php
class Math
{
	public function sum($a, $b)
	{
		if (!is_numeric($a) || !is_numeric($b)) {
			throw new InvalidArgumentException('Invalid Numbers');
		}
		// sum
		$result = $a + $b;

		if ($result > 10) {
			throw new OutOfRangeException('Result greater than 10');
		}

		return $result;
	}

}

$math = new Math();

try {
	echo $math->sum(10, 50);
} catch (InvalidArgumentException $e) {
	echo 'There was an error in the calculate: ' . $e->getMessage();
} catch (OutOfRangeException $e) {
	echo 'There was an error during workflow: ' . $e->getMessage();
}