Understanding php namespace and why the fatal error: undefined constant

Question

Trying to understand how namespace in php works and am stuck.

This below is the architecture of the project.

Class: Loader.php (suppose to load controller/model/ library but for now gibberish test codes)

namespace system\core;

class Loader
{
    public function index()
    {
        echo 'loader';
    }

    public function controller($pathtocontroller)
    {
        // Echo path to the controller
        echo $pathtocontroller;

    }
}

index.php

require 'system/core/Loader.php';
require 'system/core/BaseController.php';
require 'app/controller/common/HomeController.php';

use system\core;
use app\controller;

$loader = new \system\core\Loader();
$loader->controller(app\controller\common\HomeController);

and this is the error I get

Fatal error: Undefined constant 'app\controller\common\HomeController' in C:\xampp\htdocs\psrstd\index.php on line 20. Lin 20 on index is $loader->controller(app\controller\common\HomeController);

Expected Result: app/controller/common/HomeController

in case you wondering what's in there at the HomeController (again gibberish test code)

namespace app\controller\common;
use system\core\BaseController;

class HomeController extends BaseController
{
    public function index()
    {
        echo 'home';
    }
}

@u_mulder, the HomeController is at app/controller/common. I was simply trying to echo the path to the controller. — Mecom
– Mecom, Commented Nov 12, 2017 at 10:54
@u_mulder, load the controller like so $this->load->controller('common/HomeController'); .. — Mecom
– Mecom, Commented Nov 12, 2017 at 10:59
@u_mulder, but that is later ... Loader.php is supposed to be a class loader. — Mecom
– Mecom, Commented Nov 12, 2017 at 10:59

hassan · Accepted Answer · 2017-11-12 10:52:15Z

1

you are passing a constant type to your controller method,

you are aiming to pass an object [ dependency injection ] so you will need to instantiate your argument like :

$loader->controller(new \app\controller\common\HomeController);

otherwise you may send this argument as a string like :

$loader->controller("\\app\\controller\\common\\HomeController");

and instantiate that object within your method [ as a factory method ]

public function controller($pathtocontroller)
{
    // new $pathtocontroller and so on

}

4 Comments

Mecom Over a year ago

this worked $loader->controller("\\app\\controller\\common\\HomeController");", but looks ugly. Is there a better way?

hassan Over a year ago

what do you mean by looks ugly?

Mecom Over a year ago

\\app\\controller\\common\\HomeControll‌er .. do I need to '\\' ? My old project I use to do $this->load->controller(common/HomeController) now having to do this $this->load->controller(common\\HomeController) would look ugly ... I'll do it if there is no other way but generally asking ... can it be done any better?.

hassan Over a year ago

the backslash is the former separator for namespaces in PHP, you can not git rid of it, and since the backslash is also the escaping character so you must escape it like this `\`

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