如何将 Java 中的字节 MD5 转换为 PHP

如何将此Java代码转换为PHP？

public static String encryptMD5_Salt(String content) {
    String resultString = "";
    String appkey = "acdf,kef";
    byte[] a = appkey.getBytes();
    byte[] datSource = content.getBytes();
    byte[] b = new byte[a.length + 4 + datSource.length];
    int i;
    for (i = 0; i < datSource.length; i++) {
        b[i] = datSource[i];
    }
    b[i++] = (byte) 143;
    b[i++] = (byte) 112;
    b[i++] = (byte) 131;
    b[i++] = (byte) 143;
    for (int k = 0; k < a.length; k++) {
        b[i] = a[k];
        i++;
    }
    try {
        MessageDigest md5 = MessageDigest.getInstance("MD5");
        md5.update(b);
        resultString = new HexBinaryAdapter().marshal(md5.digest());
    } catch (Exception e) {
        e.printStackTrace();
    }
    return resultString.toLowerCase();
}

问题是我找不到在 java 中将Integer转换为byte的等效方法：

b[i++] = (byte) 143;
b[i++] = (byte) 112;
b[i++] = (byte) 131;
b[i++] = (byte) 143;

PHP代码：

$hexString = '123456';#sample value
$bkey = pack('a*',$hexString);
$bkey .= pack('N*',143,112,131,143);
$bkey = pack('a*','acdf,kef');
$re  = md5($bkey);
$re =sha1('sha256',$re);

他们得到不同的结果。