impure.echo

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.