请问个php正则表达式的用法，求高手帮忙

请教个php正则表达式的用法，求高手帮忙
想做个友情链接的检测方法，检测对方网站是不是有我的网站的友情链接，也就是判断是否有我网站的地址；

例如:我的网站的地址是www.csdn.net,

但是有些网站有时候会在链接里面加个rel="nofollow"，这样友情链接就没有意义了；

正则没好好学，问下怎么才能检测出是否加了这个呢？
有好几种情况，例如：

HTML code

<!--

Code highlighting produced by Actipro CodeHighlighter (freeware)
http://www.CodeHighlighter.com/

--><a rel="nofollow" href="http://www.csdn.net">csdn</a>

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HTML code

<!--

Code highlighting produced by Actipro CodeHighlighter (freeware)
http://www.CodeHighlighter.com/

--><a target="_blank" rel="nofollow" href="http://www.csdn.net">csdn</a>

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HTML code

<!--

Code highlighting produced by Actipro CodeHighlighter (freeware)
http://www.CodeHighlighter.com/

--><a target="_blank" rel="nofollow" href="http://www.csdn.net">csdn</a>

Copy after login

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HTML code

<!--

Code highlighting produced by Actipro CodeHighlighter (freeware)
http://www.CodeHighlighter.com/

--><a rel="nofollow" href="http://www.csdn.net" target="_blank">csdn</a>

Copy after login

HTML code

<!--

Code highlighting produced by Actipro CodeHighlighter (freeware)
http://www.CodeHighlighter.com/

--><a href="http://www.csdn.net" target="_blank" rel="nofollow">csdn</a>

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PHP code

<!--

Code highlighting produced by Actipro CodeHighlighter (freeware)
http://www.CodeHighlighter.com/

-->
$out=strtolower(@file_get_contents(http://www.xxx.com));
      if($out){
          $out=str_replace("\r\n","",$out);
          $out=str_replace("\r","",$out);
          $out=str_replace("\n","",$out);
          $havelink=preg_match_all('/<a>(.*?)/i', $out, $m);
           
          if($havelink||strstr($robots,'nofollow')){
                         echo "友情链接存在";

}
                   }


</a>

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PHP code

$array = csdn
<a target="_blank" rel="nofollow" href="http://www.csdn.net">csdn</a>
<a target="_blank" rel="nofollow" href="http://www.csdn.net">csdn</a>
<a rel="nofollow" href="http://www.csdn.net" target="_blank">csdn</a>
HTML;
preg_match_all('/(<a.>)/is', $array, $match);
if (isset($match[1])) {
    foreach ($match[1] as $html) {
        if (stripos($html, 'rel="nofollow"') !== FALSE)
            echo 'bad!';
        break;
    }

} <div class="clear">
                 
              
              
        
            </div></a.>

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