Constructor property promotion reduces DTO and service-constructor boilerplate while keeping types visible.
The examples below begin with the core behavior, then move to an application-oriented use.
How PHP Constructor Property Promotion: Real-World Examples Works
Constructor property promotion reduces DTO and service-constructor boilerplate while keeping types visible.
Example 1: Basic Usage
This example uses a small input to make the main behavior visible.
<?php
final class SendEmail { public function __construct(public readonly string $to, public readonly string $subject) {} }
echo (new SendEmail("[email protected]", "Welcome"))->subject;Output:
WelcomeConstructor property promotion reduces DTO and service-constructor boilerplate while keeping types visible.
Example 2: A Different Input
A different set of values shows the same operation in another situation.
<?php
final readonly class ProductDto { public function __construct(public string $sku, public int $stock) {} }
echo (new ProductDto("A15", 8))->stock;Output:
8Use readonly where objects should not change after construction, and validate business constraints explicitly.
Practical Example: Applying the Feature
This example shows an application-style use of the feature, with its surrounding setup visible.
<?php
final readonly class ApiResult { public function __construct(public int $statusCode, public array $data) {} }
$response = new ApiResult(200, ["count" => 4]);
echo $response->data["count"];Output:
4The code is shown for learning. Adjust the class names, inputs and error handling to suit your application.
Important Behavior and Edge Cases
- Use readonly where objects should not change after construction, and validate business constraints explicitly.
- Constructor property promotion reduces DTO and service-constructor boilerplate while keeping types visible.
- Observe differences in empty inputs, invalid states and optional extension availability where relevant.
Comparison With Related Approaches
| Approach | Important Difference |
|---|---|
PHP Constructor Property Promotion: Real-World Examples | Constructor property promotion reduces DTO and service-constructor boilerplate while keeping types visible. |
| Alternative approach | Ordinary constructors can be clearer when initialization has significant transformation logic. |
Common Beginner Mistakes
| Mistake | Correct Approach |
|---|---|
Ignoring the documented state or precondition of PHP Constructor Property Promotion: Real-World Examples | Use readonly where objects should not change after construction, and validate business constraints explicitly. |
| Expecting a different type of result | Read the declared return type and distinguish returned values from changes to the source object. |
| Assuming a related API works identically | Ordinary constructors can be clearer when initialization has significant transformation logic. |
Key Takeaways
- Constructor property promotion reduces DTO and service-constructor boilerplate while keeping types visible.
- Use readonly where objects should not change after construction, and validate business constraints explicitly.
- Use the example that matches the values, runtime version and dependencies in your application.
PHP Constructor Property Promotion: Real-World Examples is useful when its behavior matches the data structure and lifecycle of your PHP application. Choose it with a clear understanding of its preconditions and returned values.