পিএইচপি callback ফাংশন

<?php

function addition($a, $b) {
    return $a + $b;
}

function subtraction($a, $b) {
    return $a - $b;
}

function calculate($callback, $a, $b) {
    return $callback($a, $b);
}

echo calculate("addition", 20, 10);
echo "
";
echo calculate("subtraction", 20, 10);

?>