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<?php final class Options { // This is OK but why redundant initialization? // public array $stack = []; public array $stack; public function __construct(array $stack) { $this->stack = $stack; } public function __set(string $name, $value) { // if (empty($this->stack)) { // // This line below yields: object(acme\Options)#1 (0) { ["stack"]=> uninitialized(array) }. // // return; // // This line below yields: object(acme\Options)#1 (1) { ["stack"]=> array(1) { ["stack"]=> array(1) { ["one"]=> int(1) } } }. // // $this->stack = []; // } // This is solving problem but the purpose is not that also corrupting $stack structure inserting a new sub-array. // object(acme\Options)#1 (1) { ["stack"]=> array(2) { ["one"]=> int(1) ["stack"]=> array(1) { ["one"]=> int(1) } } } // $this->stack = $value; // This is indicating that __set called before (before __construct). // throw new \Exception(); // This is problematic part. $this->stack[$name] = $value; } public function __get(string $name) { // This is indicating that __get called before (before __construct). // throw new \Exception(); return $this->stack[$name] ?? null; } } var_dump(new Options(['one' => 1]));