<?php
 $key = "This is supposed to be a secret key !!!";
function keyED( $txt, $encrypt_key)
{
 $encrypt_key = md5( $encrypt_key);
 $ctr=0;
 $tmp = "";
for ( $i=0; $i<strlen( $txt); $i++)
{
  if ( $ctr==strlen( $encrypt_key))  $ctr=0;
   $tmp.= substr( $txt, $i,1) ^ substr( $encrypt_key, $ctr,1);
   $ctr++;
}
return  $tmp;
}
function encrypt( $txt, $key)
{
srand((double)microtime()*1000000);
 $encrypt_key = md5(rand(0,32000));
 $ctr=0;
 $tmp = "";
for ( $i=0; $i<strlen( $txt); $i++)
{
  if ( $ctr==strlen( $encrypt_key))  $ctr=0;
   $tmp.= substr( $encrypt_key, $ctr,1) .
  (substr( $txt, $i,1) ^ substr( $encrypt_key, $ctr,1));
   $ctr++;
}
return keyED( $tmp, $key);
}
function decrypt( $txt, $key)
{
 $txt = keyED( $txt, $key);
 $tmp = "";
for ( $i=0; $i<strlen( $txt); $i++)
{
   $md5 = substr( $txt, $i,1);
   $i++;
   $tmp.= (substr( $txt, $i,1) ^  $md5);
}
return  $tmp;
}
 $string = "Hello World !!!";
// encrypt  $string, and store it in  $enc_text
 $enc_text = encrypt( $string, $key);
// decrypt the encrypted text  $enc_text, and store it in  $dec_text
 $dec_text = decrypt( $enc_text, $key);
print "Original text :  $string <Br>";
print "Encrypted text :  $enc_text <Br>";
print "Decrypted text :  $dec_text <Br>";
?>