gistfile1.php

<?php
header("Content-Type:text/plain");
/* Escaping Challenge: Make a PHP script that (Z:) generates JavaScript code
 * that generates an HTML page containing a PHP script that (goto Z) */
 
/* The purpose of this challenge is to demonstrate how complicated escaping can
 * get when you're trying to combine 4 different languages (PHP, JavaScript,
 * HTML, and string literals). */

function js_string_escape($data)
{
	return implode(array_map(function($s){
		return (ctype_alnum($s) ? $s : sprintf("\\x%02X", ord($s)));
	}, str_split(htmlentities($data,ENT_QUOTES))));
}

echo 'document.body.innerHTML="'.js_string_escape(file_get_contents(__FILE__)).'";';