Checking user input - php

Question

I'm creating an edit page which should get called this way:
users.php?action=edit&id=5
This is my code for this:
} elseif (isset($_GET['action']) && $_GET['action'] == 'edit' && isset($_GET['id']) && is_numeric($_GET['id']) && $_GET['id'] > 0) {
As you see it's long. First a check with isset is needed. I know you can leave that out, but that way I'll get PHP notices when error reporting is set to 'E_ALL'.
I can create a function to make it shorter but that way I'll need to create too many functions as I have such code on different places in my scripts, each requiring different information.
Is there any way to make this code shorter?
Thanks!

Answer 1

Since action and id both are probably going to be used might as well set them at the top of the script:
$action = !empty($_GET['action'])?$_GET['action']:false;
$id = !empty($_GET['id'])?$_GET['id']:false;
switch ($action) {
case 'edit':
if ($id !== false) {
//processing here
}
break;
default:
echo 'No known action was passed through';
}
The initial variable declaration uses the ternary operator which is a shortened if/else as an fyi.
Extra Information
I prefer this method as appose to insane if/elseif/else statements, given that it is much easier to read and you do not have to think about your logic nearly as much, so it would make it less prone to errors.

Answer 2

You could write a function that takes an array of keys:
function check_get_params($keys) {
foreach ($keys as $key) {
if (! isset($_GET[$key]) ) {
return false;
}
}
return true;
}
Then your line above would be:
} elseif (check_get_params(array('action', 'id')) && $_GET['action'] == 'edit' && is_numeric($_GET['id'])) {
which would be cleaner as:
} elseif (check_get_params(array('action', 'id'))) {
if ($_GET['action'] == 'edit' && is_numeric($_GET['id'])) {

Answer 3

I would check parameters first:
$action = (isset($_GET['action']) && !empty($_GET['action'])) ? $_GET['action'] : false;
$id = (isset($_GET['id']) && !empty($_GET['id'])) ? $_GET['id'] : false;
settype($id, 'int'); // "123" became 123(int)
And then go with:
} elseif ($action && $id && $action == 'edit' && $id > 0) {
// here we are
}