language-benchmarks/Interpreted/ackermann-function/ack.php

<?php
function ackermann($m, $n)
{
    if ($m==0)
    {
        return $n + 1;
    }
    elseif ($n==0)
    {
        return ackermann($m-1, 1);
    }
    return ackermann($m-1, ackermann($m, $n-1));
}

echo ackermann($argv[1], $argv[2]), "\n";
?>