gistfile1.php

<?php
const WORD = 'MY FANCY WORD';
const JOKER = '\'';

$parts = [];
$i = 0;

foreach (str_split(strrev(WORD)) as $word) {
    $parts[pow(2, $i++)] = $word;
}

for ($i = 0; $i < pow(2, count($parts)); ++$i) {
    $word = '';    

    foreach ($parts as $flag => $letter) {
        $word .= $i & $flag ? $letter : JOKER;
    }

    echo strrev($word) . "\n";
}