PHP Regular Expression error,

PHP Regular expression error, Master Please enter.
$str = Preg_replace ("/(? ) *) (TEA) (?! \ "|<\/a>)/sui", ' tea ', $str, 5);

The error is as follows:
Warning:preg_replace () [Function.preg-replace]: compilation Failed:lookbehind assertion is a fixed length at offset 10 In D:\AppServ\www\Template\test.php on line 28


------Solution--------------------
Give it a try

PHP Code

        $html = <<
  <> 
   Chinese tea Here is a link to the Chinese tea panorama. Here is the existing link HTML for the tea;        echo preg_replace (' # =[^>]* (?=< (?! /a>) (|$)) Tea # ', '/', $html);    }
   
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