MiThink 记事本

<?php
$post_content = "@jb哈哈：51和@twitter@在研究用#P H        P#的#正则表达式#过   滤话题和<i></i>对象名";

// 过滤多空格，转化HTML代码
$post_content = preg_replace(['/(\s+)/', '/@/', '/</', '/>/'], [' ', ' @', '&lt;', '&gt;'], $post_content);

// 标签正则
$tag_pattern = "/\#([^\#|.]+)\#/";

// 用户正则
$user_pattern = "/@([^\r\n]*?)[:|：|，|,|#|\s]/i";

// 提取用户
preg_match_all($user_pattern, $post_content, $userArr);

// 处理用户
$test = $re = [];
foreach ($userArr[1] as $key => $user) {
    if (strlen($user) < 30 && $key < 3) {
        $test[] = "/@{$user}/";
        $re[] = "<a href='a.php?id={$user}''>@{$user}</a>";
    }
}

// 处理正文
$post_content = preg_replace($test, $re, $post_content);
$post_content = preg_replace($tag_pattern, '<a href="http://twitter.com/search?q=#${1}">#${1}#</a>', $post_content, 1);

// 输出
echo trim($post_content);