简单的BBcode parsing

<?PHP
/**
 * Basic BBCode parsing
 */
class BBcode{
	public static $bbtags = array(
		'[h1]' => '<h1>','[/h1]' => '</h1>',
		'[h2]' => '<h2>','[/h2]' => '</h2>',
		'[h3]' => '<h3>','[/h3]' => '</h3>',

		'[table]' => '<table>','[/table]' => '</table>',
		'[tr]' => '<tr>','[/tr]' => '</tr>',
		'[td]' => '<td>','[/td]' => '</td>',

		'[p]' => '<p>','[/p]' => '</p>',
		'[left]' => '<div style="text-align:left;">','[/left]' => '</div>',
		'[right]' => '<div style="text-align:right;">','[/right]' => '</div>',
		'[center]' => '<div style="text-align:center;">','[/center]' => '</div>',
		'[justify]' => '<div style="text-align:justify;">','[/justify]' => '</div>',

		'[b]' => '<b>','[/b]' => '</b>',
		'[i]' => '<i>','[/i]' => '</i>',
		'[u]' => '<u>','[/u]' => '</u>',
		'[ol]' => '<ol>','[/ol]' => '</ol>',
		'[ul]' => '<ul>','[/ul]' => '</ul>',
		'[li]' => '<li>','[/li]' => '</li>',
		'[br]' => '<br>',
		'[pre]' => '<pre>','[/pre]' => '</pre>',	     
		'[/class]' => '</div>',
	);

	public static $bbextended = array(
		//"/\n[\s| ]*\r/"=>"<br>", 
		"/\[url](.*?)\[\/url]/i" => "<a href=\"http://$1\" title=\"$1\">$1</a>",
		"/\[url=(.*?)\](.*?)\[\/url\]/i" => "<a href=\"$1\" title=\"$2\">$2</a>",
		"/\[img\]([^[]*)\[\/img\]/i" => "<img src=\"$1\" alt=\" \" />",
		"/\[img=(.*?)\](.*?)\[\/img\]/i" =>"<img src=\"$1\" alt=\"$2\"  title=\"$2\" />",
		"/\[color=(.*?)\](.*?)\[\/color\]/i" => "<font color=\"$1\" >$2</font>",
		"/\[class=(.*?)\]/" => "<div class=\"$1\">",
		//"/\[img=(.*?)\](.*?)\[\/img\]/i" => "<img src=\"$1\" class=\"$2\" />",
	);

	public static function toHtml($bbtext){
		$bbtext = Html::chars($bbtext);
		$bbtext = str_ireplace(array_keys(self::$bbtags), array_values(self::$bbtags), $bbtext);
		foreach(self::$bbextended as $match=>$replacement){
			$bbtext = preg_replace($match, $replacement, $bbtext);
		}
		return $bbtext;
	}
}