My object contains several instances of itself, should I be bothered?

Question

I have two classes: Quiz and Question :

 class Quiz() { public $quiz_id; public $quiz_name; // Arrays of objects public $questions; public $personalities; function __construct($quiz_id) { // Sets the basic data of the quiz $this->quiz_id = $quiz_id; $this->quiz_name = $quiz_name_from_db; } function LoadQuestions() { // Get question ids from database // Blank array to add questions to $array_of_question_objects = array(); foreach ($question_from_db AS $question_info) { // Create Question object, passing this Quiz object $question_object = new Question($question_info["question_id"], $this); // Add the question to the array $array_of_question_objects += $question_object; } // Set the array within the Quiz object $this->questions = $array_of_question_objects; } function LoadPersonalities() { $this->personalities = $array_of_personalty_objects; } } class Question() { public $question; // Quiz object within the question for access to personalities and quiz type private $quiz_object; function __construct($question_id, $quiz_object) { // Set the quiz object within the question $this->quiz_object; // Load the question information from the database and set the values of the class $this->question = $question_from_database; } function ShowQuestion() { // Show a question on the page and also // Loop through all of the personalities echo "<div id="question">"; if ($quiz_object->quiz_type == "personality") { foreach ($quiz_object->personalities AS $quiz_personality) { // Show each personality echo $quiz_personality; } } } } 

As you can see, I need to give my Question objects access to my Quiz object values: $quiz_type and $personalities .

If I want to download all the questions and with their possible individual results, I will use the following code:

 $quiz_id = 1; // Create a quiz object $quiz_object = new Quiz($quiz_id); // Load the questions in to the Quiz object $quiz_object->LoadQuestions(); // Load all of the personalities $quiz_object->LoadPersonalities(); // Show the questions foreach ($quiz_object->questions AS $question) { // Show the question $question->ShowQuestion(); } 

If I want to show only one question (and all information about the person), I can use the following code:

 $quiz_id = 1; $question_id = 40; // Create a quiz object $quiz_object = new Quiz($quiz_id); // Load all of the personalities for the quiz object $quiz_object->LoadPersonalities(); // Load the question as an object $question_object = new Question($question_id, $quiz_object); // Show the HTML for the question $question_object->ShowQuestion(); 

I am concerned that every object in my Question needs information from a Quiz object in order to function .

When I load all the Question objects into my quiz (using $ quiz_object-> LoadQuestions), my quiz object essentially contains the request information, as well as an instance several times for each quiz question.

So this is a bit like

Quiz_object {

 Question_object: { question information instance of `Quiz_object` } Question_object: { question information instance of `Quiz_object` } Question_object: { question information instance of `Quiz_object` } Question_object: { question information instance of `Quiz_object` } Question_object: { question information instance of `Quiz_object` } 

}

So, my Quiz object is duplicated several times inside the object.

Should I be worried about this, or is PHP handling the instance that I am passing as just an object reference?

Answer 1

Even you assign the same quiz instance to several variables, this should not be a problem at all, but it’s completely normal.

Since you have one instance here, and each variable is a way to access one instance, here in your example questions are asked, of which the quiz they are part of.

As with your design, questions should know which quiz they belong to, this is what you need to make it generally applicable.

This is a standard 1: n ratio:

  1:n quiz:questions 

Make sure that you keep the number of relationships to the minimum necessary for your application to work.

Answer 2

Don’t worry, as PHP version 5, running around objects, is executed by reference.