<?php

$subject = "my email is spark@imooc.com";

//在这里补充代码，实现正则匹配，并输出邮箱地址

$P='/my\s+email\s+is\s+(\w+@\w+\.\w+)/';（\s不是表示空字符吗啊换这种写法也是错的啊'/my email is (【\w+】@\w+\.\w+)/'）为什么啊

preg_match($p, $subject, $matches);

echo $matches[1];

为什么会报错啊？Notice: Undefined variable: p in /26/562/J3c4/index.php on line 5

Warning: preg_match(): Empty regular expression in /26/562/J3c4/index.php on line 5