Error Identifier: switch.duplicateCase

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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);

function doFoo(int $i): void
{
	switch ($i) {
		case 1:
			break;
		case 2:
			break;
		case 1:
			break;
	}
}

Why is it reported? #

A switch matches its cases from top to bottom and executes the first one that matches. When two cases have the same value, the later one can never be reached — the earlier case always wins. This is almost always a copy-paste mistake or a leftover from refactoring.

Because switch compares with loose ==, values that are only loosely equal count as duplicates too. For example 1, '1', 1.0 and true all match the same subject value and cannot be told apart by a switch:

<?php declare(strict_types = 1);

function doFoo(mixed $m): void
{
	switch ($m) {
		case 1:
			break;
		case '1': // duplicate of case 1
			break;
	}
}

How to fix it #

Remove the duplicate case if it is redundant:

 switch ($i) {
 	case 1:
 		break;
 	case 2:
 		break;
-	case 1:
-		break;
 }

If the later case was meant to match a different value, correct it:

 switch ($i) {
 	case 1:
 		break;
 	case 2:
 		break;
-	case 1:
+	case 3:
 		break;
 }

How to ignore this error #

You can use the identifier switch.duplicateCase to ignore this error using a comment:

// @phpstan-ignore switch.duplicateCase
codeThatProducesTheError();

You can also use only the identifier key to ignore all errors of the same type in your configuration file in the ignoreErrors parameter:

parameters:
	ignoreErrors:
		-
			identifier: switch.duplicateCase

Rules that report this error #

• PHPStan\Rules\Comparison\SwitchConditionRule [1]