gistfile1.php

<?php
class NumberCruncher {
    public function __call($m, $n) {
        switch($m = substr($m, -1, 1)) {
            default: return ($m == 'F') ? (9 * $this->C($n[0])) : ($n[0] * ($n[0] * 0.5));
            case 'A': return $n[0] + 4;
            case 'B': return $n[0] * 3;
            case 'D': return ($n[0] == 0) ? (1) : ($n[0] * $this->D($n[0] - 1));
            case 'E': return ($n[0] > 1) ? ($this->E($n[0] - 1) + $this->E($n[0] - 2)) : ($n[0]);
            case 'G': return $this->D($n[0]) - $this->E($n[0]);
        }
    }
}