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Error Identifier: unset.offset

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(): void
{
	$scalar = 3;
	unset($scalar['a']);
}

Why is it reported? #

The unset() call attempts to remove an array offset from a type that either does not support offset access or does not have the specified offset. This indicates a logic error – the variable is not the array that was expected, or the offset does not exist on the given type.

In the example above, $scalar is an int, which does not support offset access. Attempting to unset an offset on it is meaningless.

How to fix it #

Make sure unset() is called on a variable that supports offset access and has the given offset:

 <?php declare(strict_types = 1);
 
 function doFoo(): void
 {
-	$scalar = 3;
-	unset($scalar['a']);
+	$data = ['a' => 1, 'b' => 2];
+	unset($data['a']);
 }

Or verify the type of the variable before unsetting:

 <?php declare(strict_types = 1);
 
-/** @param iterable<int, int> $iterable */
-function doBar(iterable $iterable): void
+/** @param array<int, int> $data */
+function doBar(array $data): void
 {
-	unset($iterable['string']);
+	unset($data[0]);
 }

How to ignore this error #

You can use the identifier unset.offset to ignore this error using a comment:

// @phpstan-ignore unset.offset
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: unset.offset

Rules that report this error #

• PHPStan\Rules\Variables\UnsetRule [1]

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