Names and Scopes

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When you build a Slim application you will enter various scopes in your code (e.g. global scope and function scope). You will likely need a reference to your Slim application in each scope. There are several ways to do this:

  • Use application names with the Slim application’s getInstance() static method
  • Curry an application instance into function scope with the use keyword

Application Names

Every Slim application may be given a name. This is optional. Names help you get a reference to a Slim application instance in any scope throughout your code. Here is how you set and get an application’s name:

<?php
$app = new \Slim\Slim();
$app->setName('foo');
$name = $app->getName(); // "foo"

Scope Resolution

So how do you get a reference to your Slim application? The example below demonstrates how to obtain a reference to a Slim application within a route callback function. The $app variable is used in the global scope to define the HTTP GET route. But the $app variable is also needed within the route’s callback scope to render a template.

<?php
$app = new \Slim\Slim();
$app->get('/foo', function () {
    $app->render('foo.php'); // <-- ERROR
});

This example fails because the $app variable is unavailable inside the route callback function.

Currying

We can inject the $app variable into the callback function with the use keyword:

<?php
$app = new \Slim\Slim();
$app->get('/foo', function () use ($app) {
    $app->render('foo.php'); // <-- SUCCESS
});

Fetch by Name

You can use the Slim application’s getInstance() static method, too:

<?php
$app = new \Slim\Slim();
$app->get('/foo', 'foo');
function foo() {
    $app = Slim::getInstance();
    $app->render('foo.php');
}