如何模拟堆栈溢出自动链接行为

试试这个。URL匹配正则表达式模式来自Daring Fireball。

/**
 * Replace links in text with html links
 *
 * @param  string $text
 * @return string
 */
function auto_link_text($text)
{
   // a more readably-formatted version of the pattern is on http://daringfireball.net/2010/07/improved_regex_for_matching_urls
   $pattern  = '(?i)\b((?:[a-z][\w-]+:(?:/{1,3}|[a-z0-9%])|www\d{0,3}[.]|[a-z0-9.\-]+[.][a-z]{2,4}/)(?:[^\s()<>]+|\(([^\s()<>]+|(\([^\s()<>]+\)))*\))+(?:\(([^\s()<>]+|(\([^\s()<>]+\)))*\)|[^\s`!()\[\]{};:\'".,<>?«»“”‘’]))';

   $callback = create_function('$matches', '
       $url       = array_shift($matches);
       $url_parts = parse_url($url);

       $text = parse_url($url, PHP_URL_HOST) . parse_url($url, PHP_URL_PATH);
       $text = preg_replace("/^www./", "", $text);

       $last = -(strlen(strrchr($text, "/"))) + 1;
       if ($last < 0) {
           $text = substr($text, 0, $last) . "&hellip;";
       }

       return sprintf(\'<a rel="nofollow" href="%s">%s</a>\', $url, $text);
   ');

   return preg_replace_callback($pattern, $callback, $text);
}

输入文本：

This is my text.  I wonder if you know about asking questions on StackOverflow:
 Check This out http://www.stackoverflow.com/questions/1925455/how-to-mimic-stackoverflow-auto-link-behavior

 Also, base_convert php function?
http://pt.php.net/manual/en/function.base-convert.php#52450

http://pt.php.net/manual/en/function.base-convert.php?wtf=hehe#52450

输出文本：

This is my text.  I wonder if you know about asking questions on StackOverflow:
 Check This out <a rel="nofollow" href="http://www.stackoverflow.com/questions/1925455/how-to-mimic-stackoverflow-auto-link-behavior">stackoverflow.com/questions/1925455/&hellip;</a>

 Also, base_convert php function?
<a rel="nofollow" href="http://pt.php.net/manual/en/function.base-convert.php#52450">pt.php.net/manual/en/&hellip;</a>

<a rel="nofollow" href="http://pt.php.net/manual/en/function.base-convert.php?wtf=hehe#52450">pt.php.net/manual/en/&hellip;</a>

这基于相同的 daringfireball.net 正则表达式，但比 Eric Coleman 的示例添加了更多的逻辑，以及最大 URL 深度（SO 似乎是 50）、URL 截断时的最大路径深度（SO 似乎是 2）和省略号字符 （） 的配置。…

据我所知，这复制了所有SO URL重写功能，至少就到目前为止在这里的评论和响应中讨论的内容而言。

function auto_link_text($text) {
    $pattern  = '#\b(([\w-]+://?|www[.])[^\s()<>]+(?:\([\w\d]+\)|([^[:punct:]\s]|/)))#';
    return preg_replace_callback($pattern, 'auto_link_text_callback', $text);
}

function auto_link_text_callback($matches) {
    $max_url_length = 50;
    $max_depth_if_over_length = 2;
    $ellipsis = '&hellip;';

    $url_full = $matches[0];
    $url_short = '';

    if (strlen($url_full) > $max_url_length) {
        $parts = parse_url($url_full);
        $url_short = $parts['scheme'] . '://' . preg_replace('/^www\./', '', $parts['host']) . '/';

        $path_components = explode('/', trim($parts['path'], '/'));
        foreach ($path_components as $dir) {
            $url_string_components[] = $dir . '/';
        }

        if (!empty($parts['query'])) {
            $url_string_components[] = '?' . $parts['query'];
        }

        if (!empty($parts['fragment'])) {
            $url_string_components[] = '#' . $parts['fragment'];
        }

        for ($k = 0; $k < count($url_string_components); $k++) {
            $curr_component = $url_string_components[$k];
            if ($k >= $max_depth_if_over_length || strlen($url_short) + strlen($curr_component) > $max_url_length) {
                if ($k == 0 && strlen($url_short) < $max_url_length) {
                    // Always show a portion of first directory
                    $url_short .= substr($curr_component, 0, $max_url_length - strlen($url_short));
                }
                $url_short .= $ellipsis;
                break;
            }
            $url_short .= $curr_component;
        }

    } else {
        $url_short = $url_full;
    }

    return "<a rel=\"nofollow\" href=\"$url_full\">$url_short</a>";
}

示例输入：

This is my text.  I wonder if you know about asking questions on StackOverflow:
Check This out http://www.stackoverflow.com/questions/1925455/how-to-mimic-stackoverflow-auto-link-behavior

Also, base_convert php function?
http://pt.php.net/manual/en/function.base-convert.php#52450

http://pt.php.net/manual/en/function.base-convert.php?wtf=hehe#52450

http://a.b/c/d/e/f/test

and http://a.b/c/d/e/f/g/h/i/j/k/l/m/n/o/p/q/r/s/t/u/v/z/y/w/z/test

示例输出：

This is my text.  I wonder if you know about asking questions on StackOverflow:
Check This out <a rel="nofollow" href="http://www.stackoverflow.com/questions/1925455/how-to-mimic-stackoverflow-auto-link-behavior">http://stackoverflow.com/questions/1925455/&hellip;</a> 

Also, base_convert php function?
<a rel="nofollow" href="http://pt.php.net/manual/en/function.base-convert.php#52450">http://pt.php.net/manual/en/&hellip;</a> 

<a rel="nofollow" href="http://pt.php.net/manual/en/function.base-convert.php?wtf=hehe#52450">http://pt.php.net/manual/en/&hellip;</a> 

<a rel="nofollow" href="http://a.b/c/d/e/f/test">http://a.b/c/d/e/f/test</a> 

and <a rel="nofollow" href="http://a.b/c/d/e/f/g/h/i/j/k/l/m/n/o/p/q/r/s/t/u/v/z/y/w/z/test">http://a.b/c/d/&hellip;</a>