Replicating / Implementing Java's AES/CBC/PKCS5Padding encryption in PHP

ChecksumGen.java

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;
import java.util.Base64;
import java.io.ByteArrayOutputStream; 


public class ChecksumGen {

    public static void main(final String[] args) {
        String data = "INPUTDATA";
        String secretKey = "0000000000000000000000000000000000000000000000000000000000000000";
        byte[] iv = new byte[16];
        try {
            byte[] hashedData = getDigest(data);
            byte[] key = hexStringToByteArray(secretKey);
            byte[] checksum = encrypt(key, hashedData, iv);
            showB64("key ", key);
            showB64("iv ", iv);
            showB64("hashedData ", hashedData);
            showB64("checksum ", checksum);
        } catch (Exception ex) {
            throw new RuntimeException(ex);
        }
    }

    public static byte[] getDigest(String checkSumInput) {
        try {
            MessageDigest localMessageDigest = MessageDigest.getInstance("SHA-256");
            byte[] checkSumInputBytes = checkSumInput.getBytes("UTF-8");
            localMessageDigest.update(checkSumInputBytes);
            byte[] digest = localMessageDigest.digest();
            return digest;
        } catch (NoSuchAlgorithmException | UnsupportedEncodingException ex) {
            throw new RuntimeException(ex);
        }
    }

    public static byte[] hexStringToByteArray(String s) {
        byte[] b = new byte[s.length() / 2];
        for (int i = 0; i < b.length; i++) {
            int index = i * 2;
            int v = Integer.parseInt(s.substring(index, index + 2), 16);
            b[i] = (byte) v;
        }
        return b;
    }

    public static byte[] encrypt(byte[] key,byte[] data, byte[] iv)throws Exception{
        SecretKeySpec secretKeySpec = new SecretKeySpec(key, "AES");
        IvParameterSpec ivSpec = new IvParameterSpec(iv);
        Cipher acipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        acipher.init(Cipher.ENCRYPT_MODE, secretKeySpec,ivSpec);
        byte[] arrayOfByte1 = acipher.doFinal(data);
        return arrayOfByte1;
    }
    
    public static void showB64(String label, byte[] rawData) {
      System.out.println(label + ":" + Base64.getEncoder().encodeToString(rawData));
    }
}

/* Sample output :
key :AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=
iv :AAAAAAAAAAAAAAAAAAAAAA==
hashedData :ZAgNCUfIbdT9EjdkCb3XDNpMFGV34rXNjcTOQ9cdZ3w=
checksum :9NS/ZKMscpa4V7i2YQQPoycxCwbL1BlK3h9O/1ujoD1iYgjE8tZx+JRGflw5WikH
*/

ChecksumGen.php

<?php

/*
Following notes are from my research regarding padding (text not mine).
Read to understand the confusion between PKCS7 (default padding) and 
PKCS5 (which we are trying to achieve here) :

OPENSSL_ZERO_PADDING has a direct impact on the OpenSSL context.  EVP_CIPHER_CTX_set_padding() enables or disables padding (enabled by default).  So, OPENSSL_ZERO_PADDING disables padding for the context, which means that you will have to manually apply your own padding out to the block size.  Without using OPENSSL_ZERO_PADDING, you will automatically get PKCS#7 padding.

OPENSSL_RAW_DATA does not affect the OpenSSL context but has an impact on the format of the data returned to the caller.  When OPENSSL_RAW_DATA is specified, the returned data is returned as-is.  When it is not specified, Base64 encoded data is returned to the caller.

*/

$data  = "INPUTDATA"; 
$hashedData = hash("sha256", $data, true);
$secretKey = "0000000000000000000000000000000000000000000000000000000000000000";
$ivStr = "00000000000000000000000000000000";
$key = pack('H*', $secretKey);
$iv = pack('H*', $ivStr);
$inputData = pkcs5_pad($hashedData, 16);
showB64('key', $key);
showB64('iv', $iv);
showB64('hashedData', $hashedData);
showB64('inputData', $inputData);
$checksum = encrypt($key, $inputData, $iv);
showB64('checksum', $checksum);

function encrypt($key,$data,$iv){
  $cipher = 'AES-256-CBC';
  $options = OPENSSL_RAW_DATA|OPENSSL_ZERO_PADDING;
  $raw = openssl_encrypt(
  $data,
  $cipher,
  $key,
  $options,
  $iv
  );
  return $raw;
}

function pkcs5_pad($text, $blocksize){ 
  $pad = $blocksize - (strlen($text) % $blocksize); 
  return $text . str_repeat(chr($pad), $pad); 
}     
  
function showB64($label, $rawData) {
  echo "{$label} :".base64_encode($rawData)."\n";
}

/* Sample output :
key :AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=
iv :AAAAAAAAAAAAAAAAAAAAAA==
hashedData :ZAgNCUfIbdT9EjdkCb3XDNpMFGV34rXNjcTOQ9cdZ3w=
inputData :ZAgNCUfIbdT9EjdkCb3XDNpMFGV34rXNjcTOQ9cdZ3wQEBAQEBAQEBAQEBAQEBAQ
checksum :9NS/ZKMscpa4V7i2YQQPoycxCwbL1BlK3h9O/1ujoD1iYgjE8tZx+JRGflw5WikH
*/