assign.readOnlyProperty

Code example

<?php declare(strict_types = 1);

class Foo
{
	private readonly int $value;

	public function __construct()
	{
		$this->value = 1;
		$this->value = 2;
	}
}

Why is it reported?

A readonly property in PHP can only be assigned once. After its initial assignment, any further attempt to assign a value to it will cause a runtime error. PHPStan detects when a readonly property is assigned more than once in the constructor or across initialization paths.

In the example above, $this->value is assigned 1 and then immediately overwritten with 2. Since the property is declared as readonly, the second assignment is invalid.

How to fix it

Remove the duplicate assignment and keep only the intended one:

 <?php declare(strict_types = 1);

 class Foo
 {
 	private readonly int $value;

 	public function __construct()
 	{
-		$this->value = 1;
 		$this->value = 2;
 	}
 }

Or use conditional logic to assign the property only once:

 <?php declare(strict_types = 1);

 class Foo
 {
 	private readonly int $value;

-	public function __construct()
+	public function __construct(bool $flag)
 	{
-		$this->value = 1;
-		$this->value = 2;
+		$this->value = $flag ? 1 : 2;
 	}
 }