PHP - Why is "Index.php?action=" not recognized as "Index.php?"

All,

I'm building a front controller in PHP. In it, I say:

if (isset($_GET['action'])){
        $action=$_GET['action'];
    } else {
        $action='';
    }

I follow that with a switch statement than governs which controller is called based on the value of $action:

switch ($action){
        case '':
            require_once('Controller_Welcome.php');
            $command=new controller_Welcome();
            break;
        case 'logon':
            require_once('Controller_Logon.php');
            $command=new controller_Logon();
            break;
        default:
            require_once('Controller_Unknown.php');
            $command=new controller_Unknown();
            break;
    }
$command->execute();

This works fine. When I launch the app, the URL is http://.../Index.php? and the Controller_Welcome.php is called. If I click on the logon menu entry, I get http://.../Index.php?action=logon, and the Controller_Logon.php is called. If I manually edit the URL to set ...?action=... to some unknown value, I get Controller_Unknown.php, which is my error page. So all is well.

What I don't understand is that if I manually alter the url to show http://.../Index.php?action=, I get the error page rather than the welcome page. Why is it that php doesn't associate a url ending with ...?action= with the switch case $action='';?

(开发者_开发问答There's no logical user case when that would happen, but I still don't understand it...)

Thanks,

JDelage

PS: Var_dumping $action returns string(0) "".

Just a note that may help with readability, and further development efforts. It appears your naming convention could permit a bit more "magic", giving way for a sort of convention over configuration, and avoidance of code duplication:

define('PATH_CONTROLLERS', 'path/to/controllers/');

$action = !empty($_GET['action'])
    ? $_GET['action']
    : 'default';

switch($action){
    case 'default':
    case 'welcome':
    case 'authenticate':
        $controller_name = "controller_{$action}";
        break;
    default:
        $controller_name = 'controller_404';
        break;
}

require PATH_CONTROLLERS . "{$controller_name}.php";
$controller = new $controller_name();

$controller->execute();

Given:

// index.php

$action:          'default'
$controller_name: 'controller_default'
require():        'path/to/controllers/controller_default.php'

// index.php?action=authenticate

$action:          'authenticate'
$controller_name: 'controller_authenticate'
require():        'path/to/controllers/controller_authenticate.php'

// index.php?action=foobar

$action:          'foobar'
$controller_name: 'controller_404'
require():        'path/to/controllers/controller_404.php'

When you set ?action=, you will get a null return value for $_GET['action']. So in your scenario, the switch statement will use the default case. Like everyone said, you can always use var_dump to see the return value.

I think action is not what you think it is. This works as expected for me.

for url ending in 'action=' blank is echoed
for url ending in 'action=anything' anything is echoed


    var_dump($_GET);
    $action = $_GET['action'];

switch ($action){
        case '':
            echo "blank";
            break;
        default:
            echo $action;
            break;
    }

The behavior you describe cannot be reproduced. I used the following and the results do no demonstrate what you are describing:

<pre>
<?php

if (isset($_GET['action'])){
    $action=$_GET['action'];
} else {
    $action='';
}

var_dump($action);
echo "\n";
var_dump($_GET);
echo "\n";


switch ($action){
    case '':
        die('empty action</pre>');
    case 'logon':
        die('logon action</pre>');
    default:
        die('unknown action</pre>');
    }
?>

call:

http://host.com/test.php?action=

result:

string(0) ""

array(1) {
  ["action"]=>
  string(0) ""
}

empty action

There is something with your other code.
this one works fine and throws Controller_Welcome at empty action