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Error Identifier: instanceof.alwaysTrue

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(\stdClass $obj): void
{
	if ($obj instanceof \stdClass) {
		// always entered
	}
}

Why is it reported? #

The instanceof check always evaluates to true because the expression is already known to be of the checked type. In the example above, $obj is typed as \stdClass, so $obj instanceof \stdClass is always true. This makes the check redundant.

How to fix it #

Remove the redundant instanceof check:

 <?php declare(strict_types = 1);
 
 function doFoo(\stdClass $obj): void
 {
-	if ($obj instanceof \stdClass) {
-		// always entered
-	}
+	// Execute the code unconditionally
 }

How to ignore this error #

You can use the identifier instanceof.alwaysTrue to ignore this error using a comment:

// @phpstan-ignore instanceof.alwaysTrue
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: instanceof.alwaysTrue

Rules that report this error #

• PHPStan\Rules\Classes\ImpossibleInstanceOfRule [1]

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