通常我们会这么写：
$str = "
http://www.baidu/.com?url=www.sina.com/";
preg_match("/http:(.*)com/", $str, $matches);
print_r($matches);
结果：
Array ( [0] =>
http://www.baidu/.com?url=www.sina.com [1] => //www.baidu/.com?url=www.sina. )
非贪婪模式匹配：
$str = "
http://www.baidu/.com?url=www.sina.com/";
preg_match("/http:(.*?)com/", $str, $matches);
print_r($matches);
结果：
Array ( [0] =>
http://www.baidu/.com [1] => //www.baidu/. )
简单的说只要在一个字符后面跟上限定个数的特殊字符，匹配就是非贪婪模式了。小伙伴们是否理解了呢？