AES128, AES256 encrypt/decrypt in PHP

<?

function aes128Encrypt($key, $data) {
  if(16 !== strlen($key)) $key = hash('MD5', $key, true);
  $padding = 16 - (strlen($data) % 16);
  $data .= str_repeat(chr($padding), $padding);
  return mcrypt_encrypt(MCRYPT_RIJNDAEL_128, $key, $data, MCRYPT_MODE_CBC, str_repeat("\0", 16));
}

function aes256Encrypt($key, $data) {
  if(32 !== strlen($key)) $key = hash('SHA256', $key, true);
  $padding = 16 - (strlen($data) % 16);
  $data .= str_repeat(chr($padding), $padding);
  return mcrypt_encrypt(MCRYPT_RIJNDAEL_128, $key, $data, MCRYPT_MODE_CBC, str_repeat("\0", 16));
}

function aes128Decrypt($key, $data) {
  if(16 !== strlen($key)) $key = hash('MD5', $key, true);
  $data = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $key, $data, MCRYPT_MODE_CBC, str_repeat("\0", 16));
  $padding = ord($data[strlen($data) - 1]);
  return substr($data, 0, -$padding);
}

function aes256Decrypt($key, $data) {
  if(32 !== strlen($key)) $key = hash('SHA256', $key, true);
  $data = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $key, $data, MCRYPT_MODE_CBC, str_repeat("\0", 16));
  $padding = ord($data[strlen($data) - 1]);
  return substr($data, 0, -$padding);
}