正则过滤html中的第一个p标签,该怎么处理

<br /><div class="content"><br />                        <p class="sherry_labels" style="margin:0 ;">　<br />                        <a href="http://zj.admin5.com/" target="_blank">中介交易</a> <a href="http://seo.admin5.com/seozhenduan/" target="_blank">SEO诊断</a><a href="http://www.admin5.net/forum-494-1.html" title="淘宝客" target="_blank">淘宝客</a> <a href="http://www.etuan.com/" target="_blank">站长团购</a> <a href="http://yun.admin5.com/" title="云主机" target="_blank">云主机</a> <a href="http://v.admin5.com/" title="A5外包" target="_blank">A5外包</a><br />                        　</p><br /><p>222</p><p>333</p><p>444</p><br /></div><br />

$s =<<< TXT<br /><div class="content"><br />                        <p class="sherry_labels" style="margin:0 ;">　<br />                        <a href="http://zj.admin5.com/" target="_blank">中介交易</a> <a href="http://seo.admin5.com/seozhenduan/" target="_blank">SEO诊断</a><a href="http://www.admin5.net/forum-494-1.html" title="淘宝客" target="_blank">淘宝客</a> <a href="http://www.etuan.com/" target="_blank">站长团购</a> <a href="http://yun.admin5.com/" title="云主机" target="_blank">云主机</a> <a href="http://v.admin5.com/" title="A5外包" target="_blank">A5外包</a><br />                        　</p><br /><p>222</p><p>333</p><p>444</p><br /></div><br />TXT;

echo preg_replace('##isU', '', $s, 1);

<div class="content"><br />                        <br /><p>222</p><p>333</p><p>444</p><br /></div><br />