Callback Functions or Closures

So-called callback functions, "callables" or "closures" are used in Laravel very often, so we need to understand all the details behind their syntax.

Take a look at these Laravel examples.

You can provide the route functionality in a callback function without any Controller:

Route::get('/greeting', function () {
    return 'Hello World';
});

You can use Collections to map through data with your custom logic defined in a callback function:

$socialLinks = collect([
    'Twitter' => $user->link_twitter,
    'Facebook' => $user->link_facebook,
    'Instagram' => $user->link_instagram,
])
->filter()
->map(fn ($link, $network) => '<a href="' . $link . '">' . $network . '</a>') 
->implode(' | ');

In Eloquent, you may use the chunk() method with a closure, too:

use App\Models\Flight;
use Illuminate\Database\Eloquent\Collection;
 
Flight::chunk(200, function (Collection $flights) { 
    foreach ($flights as $flight) {
        // ...
    }
});

So, what are the main things we need to know about them?

When Can We Use Them As Parameters?

When the method is defined with the parameters types as...