<?php
    function course_correction($x, $y, $z, $speed)
    {
        if ($x * $x * $y * $y * $z > $speed) {
            $speed = $speed - 5;
        }
        return $speed;
    }

    $speed = 34;
    echo course_correction(2, 2, 2, $speed);
? >

34