php：何时在include / require_once之后使用范围解析符号（：:)？

Question

All,

I'd like to understand

I'm looking at this code sample from w3Style's front controller tutorial:

index.php

<?php
define("PAGE_DIR", dirname(__FILE__) . "/pages");
require_once "FrontController.php";
FrontController::createInstance()->dispatch();

Why is the :: required in this case?

Does it have to do with the flexibility of one day creating a different class in "FrontController.php" which would also have a method of this name? Or is it to address the case when one would have several includes of different classes, all incorporating some same method name?

Thanks,

JDelage

Answer 1

FrontController seems to be a Singleton class.

The createInstance() method is called statically (hence the ::) and creates an object instance. Then, the dispatch() method is executed on the resulting object (hence the ->).