Question

I am reading some code that looks like that:

Class_Menu.php:

<?php
    class Menu {
        private $label;
        private $link;
        private $args;

        function __construct($label, $link, $args=array()) {
            $this->label=$label;
            $this->link=$link;
            $this->args=$args;
        }
...

Note how $args is defined as an array in the __construct. Why would one choose this approach rather than define $args in the var list:

<?php
    class Menu {
        private $label;
        private $link;
        private $args=array();

        function __construct($label, $link, $args) {
            $this->label=$label;
            $this->link=$link;
            $this->args=$args;
        }
...

Answer 1

In the first example, $args is optional. The constructor can be called with only 2 arguments for $label and $link, and $args will be defined as an empty array.

In the second example, the $args parameter is required.

(opinion): I would have left $args = array() in the constructor AND when declaring the property so it’s easy to tell at a glance what type of var $args is.

<?php
    class Menu {
        private $label;
        private $link;
        private $args = array();

        function __construct($label, $link, $args=array()) {
            $this->label=$label;
            $this->link=$link;
            $this->args=$args;
        }