Question

While reading about PHP constructors, I came across the below example on this page.

<?php
    class MyClass {
        // use a unique id for each derived constructor,
        // and use a null reference to an array, 
        // for optional parameters
        function __construct($id="", $args=null) {
            // parent constructor called first ALWAYS
            /*Remaining code here*/
        }
    }

I am not able to understand why $id is set to "" and $args to null. When would I use something like this? Why can’t we just use function __construct($id, $args) {.

Answer 1

Those are default arguments. When they are not provided by the caller, they will be set to those values. Otherwise, it will be set to the caller’s values.