Replacing JAVA with PHP for PKCS5 encryption

Question

I have been tasked with replacing a legacy java system with something which runs PHP.

I am getting a little stuck on replacing the java cryptography with PHP code.

Answer 1

Both existing answers helped, but I'll post the complete solution here.

I have not seen it documented anywhere but after looking at implementations for this encryption scheme I found the key is the first 8 bytes of the encrypted hash and the IV is the last 8.

 public function get_key_and_iv($key, $salt, $reps) {
    $hash = $key . $salt;
    for ($i = 0; $i< $reps; $i++) {
      $hash = md5($hash, TRUE);
    }
    return str_split($hash,8);
  }

seems to do the trick. Which replaces pbkdf2 in my question, negates the need for and gives a value for

Then I got caught with the padding problem which James Black mentioned and managed to fix. So final code is

list($hashed_key, $iv) = get_key_and_iv($key, $salt, $reps);
// 8 is DES block size.
$pad = 8 - (strlen($plaintext) % 8);
$padded_string = $plaintext . str_repeat(chr($pad), $pad);
return mcrypt_encrypt(MCRYPT_DES, $hashed_key, $padded_string, MCRYPT_MODE_CBC, $iv);