Error Identifier: interface.traitUse

Every error reported by PHPStan has an error identifier. Here’s a list of all error identifiers. In PHPStan Pro you can see the error identifier next to each error and filter errors by their identifiers.

Code example #

<?php declare(strict_types = 1);

trait Timestampable
{
	public function getCreatedAt(): string
	{
		return '2024-01-01';
	}
}

interface EntityInterface
{
	use Timestampable;
}

Why is it reported? #

Interfaces cannot use traits in PHP. Traits provide concrete method implementations, while interfaces are meant to define a contract of method signatures without implementations. Using a trait inside an interface is a language-level error that will cause a fatal error at runtime.

How to fix it #

Declare the required methods directly in the interface as abstract method signatures:

 <?php declare(strict_types = 1);
 
 interface EntityInterface
 {
-	use Timestampable;
+	public function getCreatedAt(): string;
 }

If the trait’s functionality needs to be shared, use the trait in the implementing classes instead:

 <?php declare(strict_types = 1);
 
 interface EntityInterface
 {
-	use Timestampable;
+	public function getCreatedAt(): string;
+}
+
+class Entity implements EntityInterface
+{
+	use Timestampable;
 }

Non-ignorable error #

This error cannot be ignored using @phpstan-ignore or the ignoreErrors configuration. Non-ignorable errors indicate code that would cause a crash or a fatal error at runtime, or a fundamental problem in the analysed code that must be addressed.

Rules that report this error #

PHPStan\Rules\Classes\ExistingClassInTraitUseRule [1]

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