php 正则表达式报错，

php 正则表达式报错，高手请进。
$str = preg_replace("/(?]*)(茶叶)(?!\"|)/sui", '茶叶', $str, 5); 

报错如下：
Warning: preg_replace() [function.preg-replace]: Compilation failed: lookbehind assertion is not fixed length at offset 10 in D:\AppServ\www\Template\test.php on line 28


------解决方案--------------------
试试

PHP code

        $html = <span title="中国好茶叶">中国茶叶</span>这儿是中国茶叶大观的链接。这儿是<a href="%E5%8E%9F%E6%9C%89%E7%9A%84%E9%93%BE%E6%8E%A5.html">茶叶</a>的现有链接html;        echo preg_replace('#(?=[^>]*(?=)|$))茶叶#','<a href="%E6%96%B0%E5%8A%A0%E7%9A%84%E9%93%BE%E6%8E%A5.html">\0</a>',$html);    }<div class="clear">
                 
              
              
        
            </div>