php - ctf question @md5 What does it mean?

Question

ctf question @md5 What does it mean

<?php
$md51 = md5('QNKCDZO');
$a = @$_GET['a'];
$md52 = @md5($a);
if(isset($a)){
if ($a != 'QNKCDZO' && $md51 == $md52) {
    echo "nctf{*****************}";
} else {
    echo "false!!!";
}}
else{echo "please input a";}
?>

Answer 1

In php, @ is the symbol to ignore errors. If you have an error in the line with the @ symbol, the error will not be displayed on the web page. MD5 is an encryption function in php.

Answer 2

@In PHP, it means to ignore warning level errors thrown by the statements following it in the current line.

Answer 3

md5 is a PHP function, see PHP documentation-md5() for details.
@ means ignoring errors in subsequent expressions. For details, see PHP documentation - Error Control Operator