two / solution 2.3

<?php

$br = "\n";

$height = 15;
$radius = 4;
$width = 16;
$depth = 7;

$cylinder = 2 * 3.14159 * $radius * $height;
$cube = $height ** 3;
$rectangularPrism = $height * $width * $depth;

print_r("volume of a cylinder" . $br . "height " . $height . $br . "radius " . $radius . $br . "volume " . $cylinder . $br . $br);

print_r("volume of a cube" . $br . "height " . $height . $br . "volume " . $cube . $br . $br);

print_r("volume of a rectangular prism" . $br . "height " . $height . $br . "width " . $width . $br . "depth " . $depth . $br . "volume " . $rectangularPrism . $br . $br);

note, this solution does all three in the same place with the same measurements. you don't have to combine them.