1. Create crypto.php as following
2. Call encrypt and decrypt method as following

call methods

---

$key = uniqid();
$src = "Hello world!";

require_once('crypto.php');
$cp = new crypto();
$tag1 = $cp->encrypt($src, $key);
$tag2 = $cp->decrypt($tag1, $key);
print($src . "<br />" . $tag1 . "<br />" . $tag2);
    

crypto.php

---

<?php

class crypto {

    public function encrypt($text, $key) { 
        $src = uniqid() . $text;
        $tag = trim(base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, $src, MCRYPT_MODE_ECB, mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB), MCRYPT_RAND)))); 
        return $tag;
    } 

    public function decrypt($text, $key) { 
        $src = $text;
        $tag = trim(mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $key, base64_decode($src), MCRYPT_MODE_ECB, mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB), MCRYPT_RAND))); 
        $tag = substr($tag, 13);
        return $tag;
    } 

}

?>