PHP截取语句修改求助!高手请进

我想把以下的代码中“ http://d.zhaoxi.net/rs.php?q=”改为“ http://www.zhaoxi.net/s?wd=”，改了之后截取内容的语句也要跟着修改，我要截取百度的搜索页面底部的“相关搜索”的关键词，我自己修改不正确，郁闷中，烦请哪位高人帮忙修改正确的语句并回贴，感激不尽。谢谢！！！
PHP语句如下--
<?php
$key = "a|b|c|d";

//开始抓取百度热门关键词
$splitkey = explode("|", $key);
$keynum=count($splitkey);

for($i=0;$i<=$keynum-1;$i++)
{
$keyword=$splitkey[$i];
$keywords=iconv("UTF-8","GBK",$keyword);
$url = " http://d.zhaoxi.net/rs.php?q=".$keywords."&tn=baidu";
$openurl = @file_get_contents($url);
//$openurl=iconv("GBK","UTF-8",$openurl);

$start=strpos($openurl,"<li class=ls>1</li>");
$end=strpos($openurl,"<li class=ls>6</li>");
$len=$end-$start;
$content=substr($openurl,$start,$len); //截取得指定内容
$content2 = explode("<img", $content);
//划分数组

for($p=0; $p<4; $p++)
{

$key = $content2[$p];

$start2=strpos($key,"baidur");//取得内容的截取段

$end2=strpos($key,"</li><li class=bar>");

$len2=$end2-$start2;

$content3=substr($key,$start2,$len2); //截取得指定内容

$content3 = str_replace("baidur>","",$content3);

$content3 = str_replace("</a>","kkxzkkxz",$content3);

$content4=$content4.$content3;
}
}
//抓取百度热门关键词结束
?>

答案：<?php
 $key = "a|b|c|d";
  
 //开始抓取百度热门关键词
  $splitkey = explode("|", $key);
  $keynum=count($splitkey);
  
  for($i=0;$i<=$keynum-1;$i++)
   {
    $keyword=$splitkey[$i];
    $keywords=iconv("UTF-8","GBK",$keyword);
$url = " http://www.zhaoxi.net/s?wd=".$keywords;
    $openurl = @file_get_contents($url);
  
  
 if($openurl==''){
  
  exit('获取不到地址的内容,退出关键字抓取程序');
  
} 
 $fen_ge_string='<td nowrap class="f14">';
  $content=explode($fen_ge_string,$openurl);
  $content_count=count($content);
  $keyword_array=array();
  
if($content_count<2){
   echo "地址{$url}没有列出相关的关键字<br />";
  }else{
   for($j=1;$j<$content_count;$j++){
    $keyword_array[]=strip_tags($content[$j]);
   }
   unset($content);
   echo "对于{$keywords}获取到关键字为:";
   foreach($keyword_array as $value){
    echo $value.',';
   }
   echo '<br />';
  }
    }
   //抓取百度热门关键词结束
 ?>