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Error Identifier: impure.echo

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);

/** @phpstan-pure */
function format(string $name): string
{
	echo "Formatting: $name";
	return strtoupper($name);
}

Why is it reported? #

A function marked as @phpstan-pure contains an echo statement. Pure functions must not have side effects, and echo produces output, which is a side effect.

How to fix it #

Remove the echo statement from the pure function:

 <?php declare(strict_types = 1);
 
 /** @phpstan-pure */
 function format(string $name): string
 {
-	echo "Formatting: $name";
 	return strtoupper($name);
 }

Or remove the @phpstan-pure annotation if the function intentionally produces output.

How to ignore this error #

You can use the identifier impure.echo to ignore this error using a comment:

// @phpstan-ignore impure.echo
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: impure.echo

Rules that report this error #

• PHPStan\Rules\Pure\PureFunctionRule [1]
• PHPStan\Rules\Pure\PureMethodRule [1]

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