Error Identifier: assign.overwritten

← Back to assign.*

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(): int
{
	$a = 1;
	$a = 2;
	return $a;
}

Why is it reported? #

The value 1 assigned to $a is never read — the variable is overwritten by $a = 2 before its first value is ever used. This is a dead store: the assignment computes a value that no code observes.

The same applies to writes to an array offset, such as $a['x'] = 1; followed by $a['x'] = 2; or $a = []; before $a['x'] is read.

Unlike variable.unused, the variable itself is used later; only this particular assignment is redundant. Unlike assign.unused, another assignment replaces the value before it can be read. Dead stores like this often point to a logic error, such as forgetting to use the first value or an accidental overwrite.

This rule is part of PHPStan’s dead code analysis. It is reported at rule level 4 and above, and is currently part of Bleeding Edge.

How to fix it #

Remove the assignment whose value is never read:

 function doFoo(): int
 {
-	$a = 1;
 	$a = 2;
 	return $a;
 }

Or, if the first value should have been used, fix the logic so it is read before being overwritten:

 function doFoo(): int
 {
 	$a = 1;
+	echo $a;
 	$a = 2;
 	return $a;
 }

How to ignore this error #

You can use the identifier assign.overwritten to ignore this error using a comment:

// @phpstan-ignore assign.overwritten
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: assign.overwritten

Rules that report this error #

• PHPStan\Rules\DeadCode\UnusedVariableRule [1]