Error Identifier: offsetAssign.valueType

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);

class TypedCollection implements ArrayAccess
{
	/** @var array<int, string> */
	private array $items = [];

	public function offsetExists(mixed $offset): bool { return isset($this->items[$offset]); }
	public function offsetGet(mixed $offset): mixed { return $this->items[$offset]; }
	public function offsetSet(mixed $offset, mixed $value): void { $this->items[$offset] = $value; }
	public function offsetUnset(mixed $offset): void { unset($this->items[$offset]); }
}

function doFoo(TypedCollection $collection): void
{
	$collection[] = 123; // ERROR: TypedCollection does not accept int.
}

Why is it reported? #

The value being assigned to an offset on the object is not compatible with the type that the object accepts. The object implements ArrayAccess (or has similar offset-access capabilities), but the value being assigned does not match the expected type. In the example above, the collection expects string values but receives an int.

How to fix it #

Assign a value of the correct type:

 <?php declare(strict_types = 1);
 
 function doFoo(TypedCollection $collection): void
 {
-	$collection[] = 123;
+	$collection[] = 'hello';
 }

Or update the collection’s type to accept the value type being assigned:

 <?php declare(strict_types = 1);
 
 class TypedCollection implements ArrayAccess
 {
-	/** @var array<int, string> */
+	/** @var array<int, string|int> */
 	private array $items = [];

 	// ...
 }

How to ignore this error #

You can use the identifier offsetAssign.valueType to ignore this error using a comment:

// @phpstan-ignore offsetAssign.valueType
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: offsetAssign.valueType

Rules that report this error #

PHPStan\Rules\Arrays\OffsetAccessValueAssignmentRule [1]

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