PHP实现UBB正则替换最简单的方法

<?php
$String = "text text text [a]this is a link[/a] text text [a]this is another link[/a] text text text text";

$String = preg_replace( "/\[a\](.+?)\[\/a\]/" , "<a href=\"\\1\">\\1</a>", $String );

echo("Change to html: $String<br/ >");

$String = preg_replace( "#<a href=\"(.+?)\">(.+?)</a>#" , "[a]\\1[/a]", $String );

echo("Back to ubb: $String<br/ >");

?>