PHP Decode

<?php  
error_reporting(0);  
include "./config.php";  
include "./flag.php";  
 
$black_list = "/admin|guest|limit|by|substr|mid|or|not|ascii|char|union|select|greatest|%00|\"|benchmark|";  
$black_list .= "=|_|in|<|>|sqlauth|_|\.|\(\)|and|if|database|where|concat|insert|having|sleep/i";  
 
if(preg_match($black_list, $_GET['pass'])) exit(":P");  
 
$query = "select user from sqlauth where user='guest' and pw='{$_GET[pass]}'";  
echo "<h2>query : {$query}</h2>";  
$result = @mysqli_fetch_array(mysqli_query($con,$query));  
$admin_info =  @mysqli_fetch_array(mysqli_query($con,'select * from sqlauth where user="admin"'));  
 
if($result['user']) echo "<h2>Welcome {$result[user]}</h2>";  
 
if(($admin_info['pw'])&& $admin_info['user']===$_GET['user'] && $admin_info['pw']===$_GET['pass'])  
{  
    echo $flag;  
}  
 
highlight_file(__FILE__);  
?>