MyBB 1.8 Login-Check API

api.php

<?php
define('IN_MYBB', false);
require_once './global.php';



if($_POST["apikey"] == "YOURAPIKEYHERE")
{
	if($_GET["action"] == "login")
	{
		$query = $db->query("SELECT * FROM " . TABLE_PREFIX . " WHERE username='".$db->escape_string($_POST['username'])."'");
		if($query->num_rows == 0)
		{
			echo "USER_NOTFOUND";
		} else {
			while($result = $db->fetch_array($query))
			{
				$end_password = $result['password'];
				
				if(md5(md5($result['salt']).md5($_POST["password"])) == $end_password)
				{
					echo "OK_LOGINSUCCESS";
				} else {
					echo "FAIL_WRONGLOGINDATA";
				}
			}
		}
	}
} else {
	die("Access denied.");
}
?>

It was created for a Ingame login.
You can use the function from mybb too "validate_password_from_username".
https://github.com/mybb/mybb/blob/f6e6cadccc9ed94b5324bb57aff7fe3f3f48999f/inc/functions_user.php#L54