Why do we use ::class syntax in Laravel source code?

Since PHP 5.5, the keyword class can also be used for class name resolution. Using ClassName::class you can get a string containing the fully qualified name of the class ClassName. This is especially useful for classes that use namespaces.

<code>$app->singleton(
    Illuminate\Contracts\Http\Kernel::class,
    App\Http\Kernel::class
);

$app->singleton(
    Illuminate\Contracts\Console\Kernel::class,
    App\Console\Kernel::class
);

$app->singleton(
    Illuminate\Contracts\Debug\ExceptionHandler::class,
    App\Exceptions\Handler::class
);
</code>

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Since the fully qualified name of the class has been written in this bootstrap/app.php code, why do we need to use the ::class syntax?

Reply content:

Since PHP 5.5, the keyword class can also be used for class name resolution. Using ClassName::class you can get a string containing the fully qualified name of the class ClassName. This is especially useful for classes that use namespaces.

<code>$app->singleton(
    Illuminate\Contracts\Http\Kernel::class,
    App\Http\Kernel::class
);

$app->singleton(
    Illuminate\Contracts\Console\Kernel::class,
    App\Console\Kernel::class
);

$app->singleton(
    Illuminate\Contracts\Debug\ExceptionHandler::class,
    App\Exceptions\Handler::class
);
</code>

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Since the fully qualified name of the class has been written in this bootstrap/app.php code, why do we need to use the ::class syntax?

Someone on Zhihu gave the correct answer https://www.zhihu.com/questio...

This is the type AppHttpKernel, which is an object type of a class;

This is the class name string of the class AppHttpKernel::class, which is a string.

For this question, you first need to understand Laravel’s container concept.