Understanding the Difference Between new ClassName and ClassName::class in PHP

Discover how `new ClassName` and `ClassName::class` differ in PHP, particularly in Laravel applications, and learn which is more appropriate for your coding needs.
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Understanding the Difference Between new ClassName and ClassName::class in PHP

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This leads us to a relevant question: Are these two statements functionally the same, and is one approach more correct than the other?

Breaking Down the Two Constructs

1. Understanding new ClassName

When you use new SendJoinerReminderEmails, you are creating a new instance of the SendJoinerReminderEmails class. Here’s what happens in practice:

Instantiation: This leads to the constructor of the class being called, allowing for any necessary initialization.

Type: The result is an object of type SendJoinerReminderEmails.

2. Understanding ClassName::class

On the other hand, SendLeaverReminderEmails::class provides the fully qualified class name as a string, like App\Mails\SendLeaverReminderEmails. Here’s what this means:

String Representation: You are not creating an instance of the class. Instead, you get the class name as a string, which can be used wherever a string is required.

Use Cases: This construct is particularly useful when you need to refer to a class name without instantiating it, such as when working with dependency injection or queue jobs in Laravel.

How It Works in Laravel's Job Method

The job method in Laravel's scheduling component handles these two constructs differently:

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In this method:

If the $job parameter is a string (like the output of ClassName::class), Laravel attempts to resolve it from the service container. This ensures that any dependencies that the class may have are resolved correctly.

If it’s an instance (like what you get from new ClassName), it bypasses the container and proceeds with the instance directly.

Conclusion: Which Should You Use?

While both new ClassName and ClassName::class have their uses, it's essential to choose the right tool for the job:

Use new ClassName when you need to create an object and directly interact with it.

Use ClassName::class when you need the class name as a string, such as when scheduling jobs or using dependency injection.

For further exploration, you can use either of these in a development environment to see their outputs by executing:

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or

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Understanding the distinction between these constructs will allow you to utilize PHP's features efficiently, enhancing both your code's performance and readability.