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Error Identifier: new.resultUnused

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);

class Validator
{
	/** @phpstan-pure */
	public function __construct()
	{
	}
}

function doFoo(): void
{
	new Validator(); // ERROR: Call to new Validator() on a separate line has no effect.
}

Why is it reported? #

A new ClassName() expression appears as a standalone statement but the constructor has no side effects. The created object is not assigned to a variable, returned, or used in any way. Since the constructor is pure (or has no impure points), instantiating the object without using it has no observable effect and is likely a mistake.

How to fix it #

Use the result of the instantiation:

 <?php declare(strict_types = 1);
 
 function doFoo(): void
 {
-	new Validator();
+	$validator = new Validator();
 }

If the constructor is intended to have side effects, make sure the constructor actually performs a side effect so PHPStan recognizes it as impure:

 <?php declare(strict_types = 1);
 
 class Validator
 {
-	/** @phpstan-pure */
 	public function __construct()
 	{
+		// perform some side effect
 	}
 }

How to ignore this error #

You can use the identifier new.resultUnused to ignore this error using a comment:

// @phpstan-ignore new.resultUnused
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: new.resultUnused

Rules that report this error #

• PHPStan\Rules\DeadCode\CallToConstructorStatementWithoutImpurePointsRule [1]
• PHPStan\Rules\Methods\CallToConstructorStatementWithoutSideEffectsRule [1] [2]

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