PHP BBCode类

<?php
/**
* BBCode
* format text marked up with bbcode tags to html
*/

class BBCode {
    private static function _format_bbcode($string){
        while(preg_match('|\[([a-z]+)=?(.*?)\](.*?)\[/\1\]|',$string, $part, PREG_OFFSET_CAPTURE)){
            $part[2][0] = str_replace('"', "", $part[2][0]);
            $part[2][0] = str_replace("'", "", $part[2][0]);
            $part[3][0] = self::_format_bbcode($part[3][0]);
            switch($part[1][0]){
                //处理加粗 斜体 下划线的元素
                case 'b':
                case 'i':
                case 'u':
                $replace = sprintf('<%s> %s </%s>', $part[1][0], $part[3][0], $part[1][0]);
                break;

                //处理代码元素
                case 'code':
                $replace = '<pre>'.$part[3][0].'</pre>';
                break;

                //处理电子邮件元素
                case 'email':
                $replace = sprintf('<a href="mailto:%s"> %s </a>', $part[3][0], $part[3][0]);
                break;

                //处理大小样式
                case 'size':
                $replace = sprintf('<span style="font-size: %s"> %s </span>', $part[2][0], $part[3][0]);
                break;

                //处理引用元素
                case 'quote':
                $replace = (empty($part[2][0])) ? ('<blockquote><p>'.$part[3][0].'</p></blockquote>') : sprintf('<blockquote><p> %s wrote:<br />%s</p>' .
                            '</blockquote>', $part[2][0], $part[3][0]);
                break;

                //处理图像元素
                case 'image':
                $replace = '<img src="'.$part[3][0].'"alt="" />';
                break;

                //处理超链接
                case 'url':
                $replace = sprintf('<a href="%s"> %s </a>', (!empty($part[2][0])) ? $part[2][0] : $part[3][0], $part[3][0]);
                break;

                case 'list':
                $replace = str_replace('[*]','</li><li>',$part[3][2]);
                $replace = '<x>'.$replace;
                switch($part[2][0]){
                    case 'i':
                    $replace = str_replace('<x></li>','<ol style="list-style-type: decimal">',$replace.'</ol>');
                    break;

                    case 'A':
                    $replace = str_replace('<x></li>','<ol style="list-style-type: upper-alpha">',$replace.'</ol>');
                    break;

                    case 'a':
                    $replace = str_replace('<x></li>','<ol style="list-style-type: lower-alpha">',$replace.'</ol>');
                    break;

                    default:
                    $replace = str_replace('<x></li>','<ul>',$replace.'</ol>');
                    break;
                }

                default:
                $replace = $part[3][0];
                break;
            }
            $string = substr_replace($string, $replace, $part[0][1], strlen($part[0][0]));

        }
        return $string;

    }

    public static function format($string){
        $string = BBCode::_format_bbcode($string);

        $string = str_replace("\r\n\r\n", '</p><p>', $string);
        $string = str_replace("\n\n", '</p><p>', $string);
        $string = str_replace("\r\n", '<br />', $string);
        $string = str_replace("\n", '<br />', $string);
        $string = '<p>'.$string.'<br />';

        return $string;
    }

}

$message = (isset($_POST['message'])) ? $_POST['message'] : "";
$message = BBCode::format($message);
echo $message;

?>
<form action="" method="post">

  <textarea name="message" rows="10" cols="50" wrap="off">

  </textarea>
  <input type="submit" value="提交" />
  </form>

 

测试 ，在文本框中输入：
[b]来自江西省[/b]
[i]来自江西省[/i]
[image]simple.jpg[/image]
[size=9]字体大小为9[/size]