impure.new

Code example

<?php declare(strict_types = 1);

class Logger
{
	/** @phpstan-impure */
	public function __construct()
	{
		echo 'Logger initialized';
	}
}

/**
 * @phpstan-pure
 */
function createLogger(): Logger
{
	return new Logger();
}

Why is it reported?

A function or method marked as @phpstan-pure must not have side effects and must always return the same result for the same inputs. Instantiating a class with new is considered impure when the constructor is known to have side effects (such as writing to a file, echoing output, or modifying global state). PHPStan reports this when the constructor is explicitly marked as @phpstan-impure.

How to fix it

If the class constructor is truly side-effect-free, mark it as @phpstan-pure:

 <?php declare(strict_types = 1);

 class Logger
 {
-	/** @phpstan-impure */
+	/** @phpstan-pure */
 	public function __construct()
 	{
-		echo 'Logger initialized';
+		// no side effects
 	}
 }

Or remove the @phpstan-pure annotation from the calling function if it genuinely needs to create objects with impure constructors:

 <?php declare(strict_types = 1);

-/**
- * @phpstan-pure
- */
 function createLogger(): Logger
 {
 	return new Logger();
 }