Why AES Decrypt code doesn't work in php 7.2

I used AES for encrypt the post parameters that send from java to server with volley. I used the class shown here in my server for decrypting the post parameters:

<?php

class MCrypt {

private $hex_iv = '31323334353637383930616263646566'; # converted Java byte code in to HEX and placed it here               
private $key = '0FDOUZ.Qz'; #Same as in JAVA

function __construct() {
    $this->key = hash('sha256', $this->key, true);
    //echo $this->key.'<br/>';
}

function encrypt($str) {       
    $td = mcrypt_module_open(MCRYPT_RIJNDAEL_128, '', MCRYPT_MODE_CBC, '');
    mcrypt_generic_init($td, $this->key, $this->hexToStr($this->hex_iv));
    $block = mcrypt_get_block_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC);
    $pad = $block - (strlen($str) % $block);
    $str .= str_repeat(chr($pad), $pad);
    $encrypted = mcrypt_generic($td, $str);
    mcrypt_generic_deinit($td);
    mcrypt_module_close($td);        
    return base64_encode($encrypted);
}

function decrypt($code) {        
    $td = mcrypt_module_open(MCRYPT_RIJNDAEL_128, '', MCRYPT_MODE_CBC, '');
            
    mcrypt_generic_init($td, $this->key, $this->hexToStr($this->hex_iv));
    $str = mdecrypt_generic($td, base64_decode($code));
    $block = mcrypt_get_block_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC);
    mcrypt_generic_deinit($td);
    mcrypt_module_close($td);        
    return $this->strippadding($str);      
    
    
}

/*
  For PKCS7 padding
 */

private function addpadding($string, $blocksize = 16) {
    $len = strlen($string);
    $pad = $blocksize - ($len % $blocksize);
    $string .= str_repeat(chr($pad), $pad);
    return $string;
}

private function strippadding($string) {
    $slast = ord(substr($string, -1));
    $slastc = chr($slast);
    $pcheck = substr($string, -$slast);
    if (preg_match("/$slastc{" . $slast . "}/", $string)) {
        $string = substr($string, 0, strlen($string) - $slast);
        return $string;
    } else {
        return false;
    }
}

function hexToStr($hex)
{
    $string='';
    for ($i=0; $i < strlen($hex)-1; $i+=2)
    {
        $string .= chr(hexdec($hex[$i].$hex[$i+1]));
    }
    return $string;
}
}

?>

Also I used this code in newuser.php file:

 <?php
 .....
//decrypt 
 $encryption = new MCrypt();
 $phone= $encryption->decrypt($phoneenc);
 $password= $encryption->decrypt($passwordenc);
 $serialdivice= $encryption->decrypt($serialdiviceenc);
 $sequretyQustion= $encryption->decrypt($sequretyQustionenc);
 $sequretyAnsewr= $encryption->decrypt($sequretyAnsewrenc);
 .... ?>

Before Update php to php7.2 my code worked correctly . But for now It get error for decrypt method when I updated php. How can I fix it?

I used openssl for both java and php .It's working correctly now.