Question

preg_replace 正则表达式替换

$WEBURL="http://www.baidu.com";
$host=preg_replace("/http:\/\/([^\.]+)\.(.*)/is","\\1",$WEBURL);
echo $host."<br>";
输出为：www

$host1=preg_replace("/http:\/\/([^\.]+)\.(.*)/is","\\2",$WEBURL);
echo $host1."<br>";
输出为：baidu.com

请问如何输出：baidu

Answer 1

$WEBURL="http://www.baidu.com";
$host=preg_replace("/http:\/\/([^\.]+)\.([^\.]+)\.(.*)/is","\\2",$WEBURL);
echo $host."<br>";
输出baidu

追问

答案是对的，能稍微解释一下么？