note 95489 added to language.types.object

Initialization, Instantiation and Instances are terms that can be confusing at first. Let's try to sort it out starting with this simple class definition. <?php class User { public $first_name; public $last_name; public function __toString() { return "User [first='$this->first_name', last='$this->last_name']"; } } ?> Now create several INSTANCES of User by INSTANTIATING the User class above. <?php $user_1 = new User; // $user_1 is an INSTANCE of User $user_2 = new User; // $user_2 is an INSTANCE of User echo $user_1 . '<br>'; // User [first='', last=''] echo $user_2 . '<br>'; // User [first='', last=''] ?> Here we have (2) two INSTANCES of User, but each instance was only INSTANTIATED once - when we used the 'new' operator. And now looking at the printed output, you can see there are no values for their first or last names. This means that the objects themselves have NOT been INITIALIZED. To remedy this situation, rewrite the class definition by adding a __construct() method. <?php class User { public $first_name; public $last_name; public function __construct($first, $last) // Require first and last names when INSTANTIATING { $this->first_name = $first; // INITIALIZE $first_name; $this->last_name = $last; // INITIALIZE $last_name; } public function __toString() { return "User [first='$this->first_name', last='$this->last_name']"; } } ?> Now try it again. <?php $user_1 = new User('John', 'Doe'); // $user_i is an INSTANCE of User $user_2 = new User('Jane', 'Doe'); // $user_2 is an INSTANCE of User echo $user_1 . '<br>'; // prints: User [first='John', last='Doe'] echo $user_2 . '<br>'; // prints: User [first='Jane', last='Doe'] ?> The __construct() method is called automatically by PHP when it sees the 'new' operator. Our __construct() method above requires the first and last names to be passed in as arguments and uses them to INITIALIZE objects when INSTANTIATING new INSTANCES. ---- Server IP: 69.147.83.197 Probable Submitter: 69.19.176.172 ---- Manual Page -- http://www.php.net/manual/en/language.types.object.php Edit -- https://master.php.net/note/edit/95489 Del: integrated -- https://master.php.net/note/delete/95489/integrated Del: useless -- https://master.php.net/note/delete/95489/useless Del: bad code -- https://master.php.net/note/delete/95489/bad+code Del: spam -- https://master.php.net/note/delete/95489/spam Del: non-english -- https://master.php.net/note/delete/95489/non-english Del: in docs -- https://master.php.net/note/delete/95489/in+docs Del: other reasons-- https://master.php.net/note/delete/95489 Reject -- https://master.php.net/note/reject/95489 Search -- https://master.php.net/manage/user-notes.php