empty($_GET['variable']) blocks the script when the variable has no value

Question

I am writing quite a simple script that uses a GET parameter to define a variable in the script. So at the beginning of the script, I check that the GET parameter exists and that it's not empty (to avoid ...page.php?param=).

I wrote this piece of code (the parameter is named a) :

if (!isset($_GET['a']) || empty($_GET['a'])) {
    header("Location: https://..."); // redirect to home page
    die();
}

And it works when there is no GET parameter at all, but if there is either ?a or ?a=, then the page is just blank, even though I add an echo "some text";

I don't really understand what is going on. Could someone explain it to me?

Thank you :-)

EDIT : here is the whole code page:

<?php

if (!isset($_GET['a']) || trim($_GET['a']) == '' || $_GET['a'] == NULL) {
    header("Location: https://google.com");
    exit();
}

echo "hello";

So I should either redirect to Google.com or print "hello" but none of this happens.

Could you add the code of the page with the `echo "some text";`? — Chris, May 07 '16 at 08:05
Instead of `die();`, use `exit();` after `header(...);` function call. — Rajdeep Paul, May 07 '16 at 08:10
Possible duplicate of [PHP: Utilizing exit(); or die(); after header("Location: ");](http://stackoverflow.com/questions/8665985/php-utilizing-exit-or-die-after-headerlocation) — Rajdeep Paul, May 07 '16 at 08:10
@RajdeepPaul I replaced `die();` with `exit();`. No change in the behaviour. Also, my post is not a duplicate I think, because my question is about `empty();` rather than `die();` — Jeahel, May 07 '16 at 08:27
@RajdeepPaul `die` and `exit` are *almost* the same thing. It doesn't matter. The differences are slight and not part of this problem. — Martin, May 07 '16 at 09:06
*the page is just blank* means something is broken. Add these lines `error_reporting(E_ALL); ini_set('display_errors', 1);` at the top of your PHP script and see if it yields any error or not. — Rajdeep Paul, May 07 '16 at 09:06
@Martin The header output will be fairly different for `exit()` and `die()`. *there is a distinct difference in Header output.* is what [this answer](http://stackoverflow.com/a/20932511/5517143) said. — Rajdeep Paul, May 07 '16 at 09:10
@RajdeepPaul yes, but that answer does not relate to the issues faced in *this* question! — Martin, May 07 '16 at 09:14
@Martin You could be right, hence I made a comment and not an answer. Glad that the issue has been resolved. *Cheers!* :-) — Rajdeep Paul, May 07 '16 at 09:19

score 2 · Accepted Answer · answered May 07 '16 at 09:01

A blank page is a classic example of a PHP error. You need to set up and use PHP error logging facility like so:

error_reporting(E_ALL);
ini_set('display_errors', 1);

At the very top of your page.

Rewriting your page I would do this:

error_reporting(E_ALL);
ini_set('display_errors', 1);
if (!isset($_GET['a']) || is_null($_GET['a'])) {
    header("Location: https://google.com");
    exit();
}

echo "hello";

score -2 · Answer 2 · edited May 07 '16 at 08:09

-2

try

if (!isset($_GET['a']) || trim($_GET['a']) == "") {

check the manual for empty http://php.net/manual/en/function.empty.php

edited May 07 '16 at 08:09

Thamilhan

13,040
5
37
59

answered May 07 '16 at 08:06

MrGapo

348
3
10

The manual states that a empty string (`""`) is considered empty and should return `true`. It is what I want, so why not using `empty()`? – Jeahel May 07 '16 at 08:29

score -2 · Answer 3 · answered May 07 '16 at 08:08

-2

Try this:

if (!isset($_GET['a']) || trim($_GET['a']) == '' || $_GET['a'] == NULL) {
    header("Location: https://www.google.com"); // redirect to home page
}

answered May 07 '16 at 08:08

Deniz B.

2,532
1
18
35

That doesn't work and I don't see why `empty` is not OK. Isn't it supposed to check what you asked me to try? I also added the whole page code in my first post. – Jeahel May 07 '16 at 08:20

empty($_GET['variable']) blocks the script when the variable has no value

3 Answers3