BUUCTF [MRCTF2020]Ez_bypass 1

I put something in F12 for you  
	include 'flag.php';  
$flag='MRCTF{xxxxxxxxxxxxxxxxxxxxxxxxx}';  
if(isset($_GET['gg'])&&isset($_GET['id'])) {  
	$id=$_GET['id'];  
	$gg=$_GET['gg'];  
	if (md5($id) === md5($gg) && $id !== $gg) {  
		echo 'You got the first step';  
		if(isset($_POST['passwd'])) {  
			$passwd=$_POST['passwd'];  
			if (!is_numeric($passwd))  
			{  
				if($passwd==1234567)  
				{  
					echo 'Good Job!';  
					highlight_file('flag.php');  
					die('By Retr_0');  
				}  
				else  
				{  
					echo "can you think twice??";  
				}  
			}  
			else{  
				echo 'You can not get it !';  
			}  
		}  
		else{  
			die('only one way to get the flag');  
		}  
	}  
	else {  
		echo "You are not a real hacker!";  
	}  
}  
else{  
	die('Please input first');  
}  
}Please input first 

  - !is_numeric函数决定了passwd参数的值是数字或数字字符串，加个!就是相反的意思，如果passwd是数字字符串并等于1234567那么就会输出flag的值，如果不是那么就会进入else语句。