<?php
$str='<p>asdfasdfs</p>dsfgsdftg<p>asdfasdfs</p>sdf<p>asdfasdfs</p>sdf<p>asdfasdfs</p>';

/*贪婪模式*/
if(preg_match_all('/<p>.*<\/p>/', $str, $m1)){
	var_dump($m1);
}

/*懒惰模式*/
if(preg_match_all('/<p>.*?<\/p>/', $str, $m2)){
	var_dump($m2);
}