Laravel Application Object $app, written $app[$k] unexpectedly not error! Why?

In the laravel 5.1 .
In the Illuminatefilesystemfilesystemmanager class
In the getconfig method
actually use

$this->app['config']["filesystems.disks.{$name}"]);

Returns an array.

But

$this->app

It's an object, obviously.
Can objects use the value of an array's key values? It's syntactically wrong, but the magic is still happening.

This is the GetConfig method.

 /**     * Get the filesystem connection configuration.     *     * @param  string  $name     * @return array     */    protected function getConfig($name)    {               return $this->app['config']["filesystems.disks.{$name}"];    }

I am alone DD ($this->app);
is as follows

 /**     * Get the filesystem connection configuration.     *     * @param  string  $name     * @return array     */    protected function getConfig($name)    {        dd($this->app);        return $this->app['config']["filesystems.disks.{$name}"];    }

Output

But I dd ($this->app ' config ');

 protected function getConfig($name)    {        dd($this->app['config']["filesystems.disks.{$name}"]);        return $this->app['config']["filesystems.disks.{$name}"];    }

Then the output is as follows

In short $app is clearly an object, how can write $app [$k] this form?

Reply content:

In the laravel 5.1 .
In the Illuminatefilesystemfilesystemmanager class
In the getconfig method
actually use

$this->app['config']["filesystems.disks.{$name}"]);

Returns an array.

But

$this->app

It's an object, obviously.
Can objects use the value of an array's key values? It's syntactically wrong, but the magic is still happening.

This is the GetConfig method.

 /**     * Get the filesystem connection configuration.     *     * @param  string  $name     * @return array     */    protected function getConfig($name)    {               return $this->app['config']["filesystems.disks.{$name}"];    }

I am alone DD ($this->app);
is as follows

 /**     * Get the filesystem connection configuration.     *     * @param  string  $name     * @return array     */    protected function getConfig($name)    {        dd($this->app);        return $this->app['config']["filesystems.disks.{$name}"];    }

Output

But I dd ($this->app ' config ');

 protected function getConfig($name)    {        dd($this->app['config']["filesystems.disks.{$name}"]);        return $this->app['config']["filesystems.disks.{$name}"];    }

Then the output is as follows

In short $app is clearly an object, how can write $app [$k] this form?

The app inherits from IlluminateContainerContainer , and Container implements it ArrayAccess (Http://php.net/manual/zh/clas ... Interface The Arrayaccess interface provides the ability to access an object like an array, as long as several methods of implementing the interface can invoke Isset, unset, [] to access the value.

$this->app['config']IlluminateConfigRepositoryIt also implements the arrayaccess, so it can also be used as an array.

ArrayAccess

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