PHP

composer autoload psr-4

"autoload": {
   "psr-4": {
        "Vendor": "src/"
    },
 },

custom autoload without composer php psr4

<?php
//custom autoload without composer
$to_map = [
    'App' =>  'app/',
    'Core' => 'Core/',
];

foreach($to_map as $prefix => $base_dir)
{
    spl_autoload_register(function ($class) use ($prefix, $base_dir) {

        $base_dir = __DIR__ . "/{$base_dir}";

        $len = strlen($prefix);
        if (strncmp($prefix, $class, $len) !== 0)
        {
            return;
        }

        $relative_class = substr($class, $len);

        $file = $base_dir . str_replace('', '/', $relative_class) . '.php';

        if (file_exists($file))
        {
            require $file;
        }
    });
}