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Error Identifier: property.inInterface

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);

interface HasName
{
	public string $name; // ERROR: Interfaces can include properties only on PHP 8.4 and later.
}

Why is it reported? #

Before PHP 8.4, interfaces cannot declare properties. Property declarations in interfaces are a PHP 8.4 feature that works together with property hooks, allowing interfaces to define abstract hooked properties that implementing classes must provide.

This error is not ignorable because it represents a PHP language-level constraint.

How to fix it #

If running PHP 8.4 or later, declare the property as a hooked property in the interface:

 <?php declare(strict_types = 1);
 
 interface HasName
 {
-	public string $name;
+	public string $name { get; set; }
 }

On earlier PHP versions, use getter and setter methods instead:

 <?php declare(strict_types = 1);
 
 interface HasName
 {
-	public string $name;
+	public function getName(): string;
+	public function setName(string $name): void;
 }

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\Properties\PropertiesInInterfaceRule [1]

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