haandy haak assist (hide javascript in image file)

<?php
//note: only works if you can change the image file mimetype to text/html;
//send me a message if you like this code

function gp_c($img, $id1){
    $pos=strpos($img, $id1);
    $o1="";
    if($pos)
        $o1=substr($img, $pos+4, ord($img[$pos-1])+(ord($img[$pos-2])*256)+(ord($img[$pos-3])*65536)+(ord($img[$pos-4])*16777216));
    return $o1;
}

function int2_4chr($N){
    if($N > 4294967295)
    return "\xff\xff\xff\xff";
    $chr0=floor($N/16777216);
    $mun=$N-($chr0*16777216);
    $chr1=floor($mun/65536);
    $mun-=($chr1*65536);
    $chr2=floor($mun/256);
    return chr($chr0).chr($chr1).chr($chr2).chr($mun-($chr2*256));
}

$IEND_r="\x82\x60B\xAEDNEI\x00\x00\x00\x00";

if(isset($_POST["txt"])){
    $img1=base64_decode("iVBORw0KGgoAAAANSUhEUgAAAAcAAAAHCAIAAABLMMCEAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsMAAA7DAcdvqGQAAABESURBVBhXY/gPAT8b/n9iAJFgwPD/z34QHxn92Q9lAQGcBDEgFBqCUptXMby6ByJhomB7Pj1nOLgDRIJEfzZgs+3PfgDFYGK3vJzbHAAAAABJRU5ErkJggg==");
    $d03i=$_POST["txt"];
    $d03l=strlen($d03i);
    if($d03l < 120001){
    $d03=int2_4chr($d03l)."ItXt".$d03i.int2_4chr(crc32("ItXt".$d03i));
    $IDp=strpos($img1, "IDAT")-4;
    $d04=substr($img1, 0, $IDp).$d03.substr($img1, $IDp);

        echo ('image file data in base64: "'.base64_encode($d04).'"<br>');
}

}

echo '<br><form method="post"><textarea name="txt" ></textarea><br><input type="submit" value="create file"></form>';






?>