替换 PHP 5.3 中的 UTF-8 字符

为什么这个测试用例不起作用？

<?php
// cards with cyrillic inidices and suits in UTF-8 encoding
$a = array('7♠', 'Д♠', 'К♠', '8♦', 'В♦', 'Д♦', '10♣', '10♥', 'В♥', 'Т♥');
foreach ($a as $card) {
        $suit = substr($card, -1);
        $card = preg_replace('/('d+)♥/', '<span class="red">$1&hearts;</span>', $card);
        $card = preg_replace('/('d+)♦/', '<span class="red">$1&diams;</span>', $card);
        $card = preg_replace('/('d+)♠/', '<span class="black">$1&spades;</span>', $card);
        $card = preg_replace('/('d+)♣/', '<span class="black">$1&clubs;</span>', $card);
        printf("suit: %s, html: %s'n", $suit, $card);
}
?>

输出：

suit: ▒, html: <span class="black">7&spades;</span>
suit: ▒, html: Д♠
suit: ▒, html: К♠
suit: ▒, html: <span class="red">8&diams;</span>
suit: ▒, html: В♦
suit: ▒, html: Д♦
suit: ▒, html: <span class="black">10&clubs;</span>
suit: ▒, html: <span class="red">10&hearts;</span>
suit: ▒, html: В♥
suit: ▒, html: Т♥

即我在 PHP 脚本中遇到 2 个问题：

1. 为什么没有正确提取最后一个 UTF-8 字符？
2. 为什么只有第一套西装被preg_replace取代？

使用 PHP 5.3.3，PostgreSQL 8.4.12 在 CentOS 6.2 上持有 UTF-8 JSON（带有俄语文本和卡片花色）。

如果 1. 是 PHP 5.3.3 中的错误，那么有没有好的解决方法？（我不想升级库存包）。

更新：

<?php
$a = array('7♠', 'Д♠', 'К♠', '8♦', 'В♦', 'Д♦', '10♣', '10♥', 'В♥', 'Т♥');
foreach ($a as $card) {
        $suit = mb_substr($card, -1, 1, 'UTF-8');
        $card = preg_replace('/('d+)♥/u', '<span class="red">$1&hearts;</span>', $card);
        $card = preg_replace('/('d+)♦/u', '<span class="red">$1&diams;</span>', $card);
        $card = preg_replace('/('d+)♠/u', '<span class="black">$1&spades;</span>', $card);
        $card = preg_replace('/('d+)♣/u', '<span class="black">$1&clubs;</span>', $card);
        printf("suit: %s, html: %s'n", $suit, $card);
}
?>

新输出：

suit: ♠, html: <span class="black">7&spades;</span>
suit: ♠, html: Д♠
suit: ♠, html: К♠
suit: ♦, html: <span class="red">8&diams;</span>
suit: ♦, html: В♦
suit: ♦, html: Д♦
suit: ♣, html: <span class="black">10&clubs;</span>
suit: ♥, html: <span class="red">10&hearts;</span>
suit: ♥, html: В♥