unset.readOnlyProperty - Phpstan

Code example

php

<?php declare(strict_types = 1);

class User
{
	public function __construct(
		public readonly string $name,
	)
	{
	}
}

function doFoo(User $user): void
{
	unset($user->name);
}

Why is it reported?

The unset() call targets a property that is declared as readonly. PHP does not allow unsetting readonly properties outside of the constructor scope. Attempting to do so results in a fatal error at runtime.

This error is also reported for properties marked with @readonly or @immutable PHPDoc tags.

How to fix it

Remove the unset() call and use a different approach to handle the absence of the value. If the property needs to be nullable, change the type and assign null instead:

diff-php

 <?php declare(strict_types = 1);

 class User
 {
 	public function __construct(
-		public readonly string $name,
+		public readonly ?string $name,
 	)
 	{
 	}
 }

-function doFoo(User $user): void
+function createUser(?string $name): User
 {
-	unset($user->name);
+	return new User($name);
 }

If the property should be mutable, remove the readonly modifier:

diff-php

 <?php declare(strict_types = 1);

 class User
 {
 	public function __construct(
-		public readonly string $name,
+		public string $name,
 	)
 	{
 	}
 }