PHP Composer Autoloader类未找到异常

|src
    |Database
        |Core
            |MysqL.PHP
        |Support
    start.PHP
|vendor
composer.json
index.PHP

MysqL.PHP文件：

<?PHP
namespace Database\Core;
//Some methods here

index.PHP和start.PHP文件：

//start.PHP file
<?PHP
require __DIR__ . '/../vendor/autoload.PHP';
?>

//index.PHP file
<?PHP
use Database\Core;
require __DIR__ . '/src/start.PHP';

$MysqL = new MysqL(); // Gets exception Class 'MysqL' cannot found etc.
?>

最后我的composer.json自动加载部分：

"autoload": {
    "psr-4": "Database\\": "src/" // Also tried "src/Database" too
}

问题出在哪儿？我真的厌倦了试图应对这种情况.请帮帮我们！谢谢.