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Error Identifier: closure.unusedUse

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(string $used, string $unused): void
{
	$fn = function () use ($used, $unused) {
		echo $used;
	};
}

Why is it reported? #

The anonymous function (closure) imports the variable $unused via the use clause, but never references it within the closure body. Importing unused variables into a closure is unnecessary and makes the code harder to understand. It may also indicate a mistake where the variable was intended to be used but was forgotten.

How to fix it #

Remove the unused variable from the use clause:

 <?php declare(strict_types = 1);
 
 function doFoo(string $used, string $unused): void
 {
-	$fn = function () use ($used, $unused) {
+	$fn = function () use ($used) {
 		echo $used;
 	};
 }

Or use the variable inside the closure if it was intended to be used:

 <?php declare(strict_types = 1);
 
 function doFoo(string $used, string $unused): void
 {
 	$fn = function () use ($used, $unused) {
 		echo $used;
+		echo $unused;
 	};
 }

How to ignore this error #

You can use the identifier closure.unusedUse to ignore this error using a comment:

// @phpstan-ignore closure.unusedUse
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: closure.unusedUse

Rules that report this error #

• PHPStan\Rules\Classes\UnusedConstructorParametersRule [1]
• PHPStan\Rules\Functions\UnusedClosureUsesRule [1]

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