Autoload

composer.json

{
    "autoload": {
        "psr-4": {
            "App\\": "./"
        }
    }
}

Foo.php

<?php

namespace App;

class Foo
{
}

class Bar
{
}

testko.php

<?php

require __DIR__ . '/vendor/autoload.php';

// This will not work, the class App\Bar cannot be autoloaded,
// it used to work with composer 1 when the autoload was optimized into a classmap
new App\Bar();

testok.php

<?php

require __DIR__ . '/vendor/autoload.php';

// This works, the file Foo.php is required by autoloading App\Foo
new App\Foo();
new App\Bar();