I am wondering how to translate this perl code to php. It seems the
md5 function is the same when using hexadecimal in perl but I'm not
sure what this md5->add code does.

Perl:
my $md5ShopPassString = Digest::MD5->new;
$md5ShopPassString->add("$ShopId");
$md5ShopPassString->add("$OrderId");
$ShopPassString = $md5ShopPassString->hexdigest;

PHP:
md5($ShopId . $OrderId);

These are not equal. Thanks in advance for any .