Error Identifier: trait.duplicateConstant

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 MyTrait
{
    public const FOO = 1;
    public const FOO = 2;
}

Why is it reported? #

A constant with the same name is declared more than once within the same trait. PHP does not allow redeclaring a constant within the same class-like structure, and this will cause a fatal error at runtime.

Traits gained support for constants in PHP 8.2. Like classes, they cannot contain duplicate constant declarations.

How to fix it #

Remove the duplicate constant declaration and keep only one:

 <?php declare(strict_types = 1);
 
 trait MyTrait
 {
     public const FOO = 1;
-    public const FOO = 2;
 }

If you need different constant values, give them different names:

 <?php declare(strict_types = 1);
 
 trait MyTrait
 {
     public const FOO = 1;
-    public const FOO = 2;
+    public const BAR = 2;
 }

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\DuplicateDeclarationRule [1]

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