Error Identifier: identical.alwaysFalse

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 $i): void
{
	if ($i === 'hello') {
		// ...
	}
}

Why is it reported? #

A strict comparison using === between two values of incompatible types will always evaluate to false. The === operator checks both value and type equality, so comparing an int with a string can never be true.

In the example above, $i is an int and 'hello' is a string. These types can never be identical, so the condition will never be satisfied and the code inside the if block is dead code.

How to fix it #

Fix the comparison to use the correct type:

 <?php declare(strict_types = 1);
 
 function doFoo(int $i): void
 {
-	if ($i === 'hello') {
+	if ($i === 42) {
 		// ...
 	}
 }

Or fix the parameter type if the comparison is correct:

 <?php declare(strict_types = 1);
 
-function doFoo(int $i): void
+function doFoo(string $i): void
 {
 	if ($i === 'hello') {
 		// ...
 	}
 }

How to ignore this error #

You can use the identifier identical.alwaysFalse to ignore this error using a comment:

// @phpstan-ignore identical.alwaysFalse
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: identical.alwaysFalse

Rules that report this error #

PHPStan\Rules\Comparison\StrictComparisonOfDifferentTypesRule [1]

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