为啥使用file_get_contents获取不到百度竞价内容

为什么使用file_get_contents获取不到百度竞价内容
$url = 'http://www.baidu.com/s?wd=%E4%BF%9D%E5%81%A5%E5%93%81&rsv_spt=1&issp=1&f=8&rsv_bp=0&rsv_idx=2&ie=utf-8&tn=baiduhome_pg&rsv_enter=0&inputT=2625&rsv_pq=f8ac4a3700000dd9&rsv_t=54ffCzY5xNXYlNcEjuJTNfBzIrJob0iUn2whzhsN7JtTaA6R0Z7yxIGlNFSR5t0vyOID&rsv_sug3=5&rsv_sug1=4&rsv_sug2=0&rsv_sug4=4274';  
$info=file_get_contents($url);
echo $info;
?>


我想获取百度竞价排名前三的几个站，使用file_get_contents输出了百度搜索结果页的内容但是为什么竞价内容不显示啊？

原来是这个的有竞价位的

但是我输出的就没有了竞价内容了请问下各位高手是什么原因啊？





------解决思路----------------------

<br /><?php<br />	$url = 'http://www.baidu.com/s?rsv_bp=0&rsv_spt=3&ie=utf-8&rsv_sug3=23&rsv_sug4=267&rsv_sug1=22&rsv_sug2=0&inputT=18&wd=%E4%BF%9D%E5%81%A5%E5%93%81&tn=89040009_1_pg';<br />    $ch = curl_init();<br />    curl_setopt($ch, CURLOPT_USERAGENT, 'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/31.0.1650.63 Safari/537.36');<br />    curl_setopt($ch, CURLOPT_URL, $url);<br />    curl_setopt($ch, CURLOPT_HEADER, 0);<br />    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);<br />    $content = curl_exec($ch);<br />    curl_close($ch);<br /><br />	echo $content;<br />

大概检查了下，百度验证了user-agent，如果为空就没有竞价那一块
------解决思路----------------------

header('Content-type: text/html;charset=utf-8');<br />$url = 'http://www.baidu.com/s?wd=%E4%BF%9D%E5%81%A5%E5%93%81&rsv_spt=1&issp=1&f=8&rsv_bp=0&rsv_idx=2&ie=utf-8&tn=baiduhome_pg&rsv_enter=0&inputT=2625&rsv_pq=f8ac4a3700000dd9&rsv_t=54ffCzY5xNXYlNcEjuJTNfBzIrJob0iUn2whzhsN7JtTaA6R0Z7yxIGlNFSR5t0vyOID&rsv_sug3=5&rsv_sug1=4&rsv_sug2=0&rsv_sug4=4274';  <br /><br />$opts = array( <br />  'http'=>array( <br />    'user_agent' => $_SERVER['HTTP_USER_AGENT']<br />  ) <br />); <br />$context = stream_context_create($opts);<br /><br />$info=file_get_contents($url, false, $context);<br />echo $info;