PHP OOP：创建全局消息数组

Question

I am trying to display an array of messages at the end of my PHP class. My message handler is working, but only if I "add_message" from within the main parent class and not if I call this function from within a child class. Sorry if this is vague but was not sure how to word the question.

TLDR; How can I add a message from within class Example?

---

MAIN PARENT CLASS

class Init {

    public function __construct() {
        $this->load_dependencies();
        $this->add_messages();
        $this->add_msg_from_instance();
    }

    private function load_dependencies() {
        require_once ROOT . 'classes/class-messages.php';
        require_once ROOT . 'classes/class-example.php';
    }

    public function add_messages() {
        $this->messages = new Message_Handler();
        $this->messages->add_message( 'hello world' );
    }

    // I Would like to add a message from within this instance....
    public function add_msg_from_instance() {
        $example = new Example();
        $example->fire_instance();
    }

    public function run() {
        $this->messages->display_messages();
    }

}

---

MESSAGE HANDLER

class Message_Handler {

    public function __construct() {
        $this->messages = array();
    }

    public function add_message( $msg ) {
        $this->messages = $this->add( $this->messages, $msg );
    }

    private function add( $messages, $msg ) {
        $messages[] = $msg;
        return $messages;
    }


    // Final Function - Should display array of all messages
    public function display_messages() {
        var_dump( $this->messages );
    }

}

EXAMPLE CLASS

class Example {
    public function fire_instance() {
        $this->messages = new Message_Handler();
        $this->messages->add_message( 'Hello Universe!' ); // This message is NOT being displayed...
    }
}

Answer 1

Because you want to keep the messages around different object, you should pass the object or use a static variable.

I would use a static variable like so:

class Init {
    public function __construct() {
        $this->load_dependencies();
        $this->add_messages();
        $this->add_msg_from_instance();
    }

    private function load_dependencies() {
        require_once ROOT . 'classes/class-messages.php';
        require_once ROOT . 'classes/class-example.php';
    }

    public function add_messages() {
        // renamed the message handler variable for clarity
        $this->message_handler = new Message_Handler();
        $this->message_handler->add_message( 'hello world' );
    }

    // I Would like to add a message from within this instance....
    public function add_msg_from_instance() {
        $example = new Example();
        $example->fire_instance();
    }

    public function run() {
        $this->message_handler->display_messages();
    }
}

class Message_Handler {
    // use a static var to remember the messages over all objects
    public static $_messages = array();

    // add message to static
    public function add_message( $msg ) {
        self::$_messages[] = $msg;
    }

    // Final Function - Should display array of all messages
    public function display_messages() {
        var_dump( self::$_messages );
    }
}

class Example {
    public function fire_instance() {
        // new object, same static array
        $message_handler = new Message_Handler();
        $message_handler->add_message( 'Hello Universe!' );
    }
}

// testing...
new Init();
new Init();
$init = new Init();
$init->add_msg_from_instance();
$init->add_msg_from_instance();
$init->add_msg_from_instance();
$init->run();