[HaBo]

function RC4($key, $data) { //encrypt and decrypt $data with the key in $keyfile with an rc4 algorithm
   $pwd = $key;
   $pwd_length = strlen($pwd);
   $key = array();

   for ($i = 0; $i < 256; $i++) {
      $key[$i] = ord($pwd{$i % $pwd_length});
      $counter[$i] = $i;
   }
   for ($i = 0; $i < 256; $i++) {
      $x = ($x + $counter[$i] + $key[$i]) % 256;
      $temp_swap = $counter[$i];
      $counter[$i] = $counter[$x];
      $counter[$x] = $temp_swap;
   }

   for ($a = $j = $i = 0; $i < strlen($data); $i++) {
      $a = ($a + 1) % 256;
      $j = ($j + $counter[$a]) % 256;
      $temp = $counter[$a];
      $counter[$a] = $counter[$j];
      $counter[$j] = $temp;
      $k = $counter[(($counter[$a] + $counter[$j]) % 256)];
      $Zcipher = ord($data{$i}) ^ $k;
      $Zcrypt .= chr($Zcipher);
   }
   return $Zcrypt;
}