PHP implements AES encryption class definition and usage

<?php
class CryptAES
{
 protected $cipher = MCRYPT_RIJNDAEL_128;
 protected $mode = MCRYPT_MODE_ECB;
 protected $pad_method = NULL;
 protected $secret_key = &#39;&#39;;
 protected $iv = &#39;&#39;;
 public function set_cipher($cipher)
 {
 $this->cipher = $cipher;
 }
 public function set_mode($mode)
 {
 $this->mode = $mode;
 }
 public function set_iv($iv)
 {
 $this->iv = $iv;
 }
 public function set_key($key)
 {
 $this->secret_key = $key;
 }
 public function require_pkcs5()
 {
 $this->pad_method = &#39;pkcs5&#39;;
 }
 protected function pad_or_unpad($str, $ext)
 {
 if ( is_null($this->pad_method) )
 {
  return $str;
 }
 else
 {
  $func_name = __CLASS__ . &#39;::&#39; . $this->pad_method . &#39;_&#39; . $ext . &#39;pad&#39;;
  if ( is_callable($func_name) )
  {
  $size = mcrypt_get_block_size($this->cipher, $this->mode);
  return call_user_func($func_name, $str, $size);
  }
 }
 return $str;
 }
 protected function pad($str)
 {
 return $this->pad_or_unpad($str, &#39;&#39;);
 }
 protected function unpad($str)
 {
 return $this->pad_or_unpad($str, &#39;un&#39;);
 }
 public function encrypt($str)
 {
 $str = $this->pad($str);
 $td = mcrypt_module_open($this->cipher, &#39;&#39;, $this->mode, &#39;&#39;);
 if ( empty($this->iv) )
 {
  $iv = @mcrypt_create_iv(mcrypt_enc_get_iv_size($td), MCRYPT_RAND);
 }
 else
 {
  $iv = $this->iv;
 }
 mcrypt_generic_init($td, $this->secret_key, $iv);
 $cyper_text = mcrypt_generic($td, $str);
 //$rt=base64_encode($cyper_text);
 $rt = bin2hex($cyper_text);
 mcrypt_generic_deinit($td);
 mcrypt_module_close($td);
 return $rt;
 }
 public function decrypt($str){
 $td = mcrypt_module_open($this->cipher, &#39;&#39;, $this->mode, &#39;&#39;);
 if ( empty($this->iv) )
 {
  $iv = @mcrypt_create_iv(mcrypt_enc_get_iv_size($td), MCRYPT_RAND);
 }
 else
 {
  $iv = $this->iv;
 }
 mcrypt_generic_init($td, $this->secret_key, $iv);
 $decrypted_text = mdecrypt_generic($td, self::hex2bin($str));
 //$decrypted_text = mdecrypt_generic($td, base64_decode($str));
 $rt = $decrypted_text;
 mcrypt_generic_deinit($td);
 mcrypt_module_close($td);
 return $this->unpad($rt);
 }
 public static function hex2bin($hexdata) {
 $bindata = &#39;&#39;;
 $length = strlen($hexdata);
 for ($i=0; $i < $length; $i += 2)
 {
  $bindata .= chr(hexdec(substr($hexdata, $i, 2)));
 }
 return $bindata;
 }
 public static function pkcs5_pad($text, $blocksize)
 {
 $pad = $blocksize - (strlen($text) % $blocksize);
 return $text . str_repeat(chr($pad), $pad);
 }
 public static function pkcs5_unpad($text)
 {
 $pad = ord($text{strlen($text) - 1});
 if ($pad > strlen($text)) return false;
 if (strspn($text, chr($pad), strlen($text) - $pad) != $pad) return false;
 return substr($text, 0, -1 * $pad);
 }
}
?>

require_once("CryptAES.class.php");
$keyStr = 'ss4fs4skfhksk';
$aes = new CryptAES();
$keyStr = $aes->hex2bin($keyStr);
$aes->set_key($keyStr);
$aes->require_pkcs5();
$d = $aes->encrypt($data);