三項演算子で、条件判定し、trueならぞろ目と表示させています。
<?php
$dice = mt_rand(1, 6);
$dice2 = mt_rand(1, 6);
$zorome = ($dice == $dice2) ? true: false;
?>
<!DOCTYPE html>
<html lang="ja">
<head>
<meta charset="utf-8">
<title>さいころ</title>
<script src="http://code.jquery.com/jquery-1.9.1.min.js"></script>
</head>
<body>
<h1>サイコロ</h1>
<p>サイコロの目は「<?php echo $dice; ?>」と「<?php echo $dice2; ?>」でした！</p>
<?php if ($zorome == true): ?>
ぞろ目です！
<?php endif; ?>
<p><a href="<?php echo $_SERVER["SCRIPT_NAME"]; ?>">もう一度！</a></p>
</body>
</html>
mt_rand()はrand()より、4倍処理が速いとphpのドキュメントに記載があります。
php mt_rand()
/*
Many random number generators of older libcs have dubious or unknown characteristics and are slow. By default, PHP uses the libc random number generator with the rand() function. The mt_rand() function is a drop-in replacement for this. It uses a random number generator with known characteristics using the » Mersenne Twister, which will produce random numbers four times faster than what the average libc rand() provides.
*/
