Error Identifier: arrayUnpacking.stringOffset

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);

$a = [1, 2, 3];
$b = ['key' => 'value'];

$merged = [...$a, ...$b];

Why is it reported? #

Before PHP 8.1, array unpacking with the spread operator (...) only supported arrays with integer keys. Using array unpacking on an array with string keys results in a fatal error in PHP versions prior to 8.1.

In the example above, $b has the string key 'key', so unpacking it with ...$b is not supported on the configured PHP version.

How to fix it #

Use array_merge() instead of array unpacking when dealing with string-keyed arrays:

 <?php declare(strict_types = 1);
 
 $a = [1, 2, 3];
 $b = ['key' => 'value'];

-$merged = [...$a, ...$b];
+$merged = array_merge($a, $b);

Or upgrade the project’s PHP version to 8.1 or later, which supports array unpacking with string keys. Update the phpVersion setting in the PHPStan configuration accordingly.

How to ignore this error #

You can use the identifier arrayUnpacking.stringOffset to ignore this error using a comment:

// @phpstan-ignore arrayUnpacking.stringOffset
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: arrayUnpacking.stringOffset

Rules that report this error #

PHPStan\Rules\Arrays\ArrayUnpackingRule [1]

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