Getting confused with empty, isset, !empty, !isset

Question

I have the following which doesn't work properly as $_GET['category'] can also equal 0.

if ( empty( $_GET['category'] ) ){
    // do something
} else {
    // do something else
}

How do I re-write this if statement to do 3 different things

Do something if $_GET['category'] does not exist at all
Do something if $_GET['category'] == 0
Do something if $_GET['category'] == something other than "does not exist" and 0.

I've tried different combinations of empty(), !empty(), isset(), !isset() but I'm not getting the results I'm after. I'm probably doing the wrong combinations...

possible duplicate of [Why check both isset() and !empty()](http://stackoverflow.com/questions/4559925/why-check-both-isset-and-empty) — KARASZI István, Oct 04 '11 at 11:45
Your requirements seem to conflict: point 3 is the counterpart of point 1 and 2. Therefor point 1, 2 and 3 combined will match all cases. Did you mean point 3 should `do something else` by any chance? — Decent Dabbler, Oct 04 '11 at 11:46

lonesomeday · Accepted Answer · 2011-10-04T12:28:28.743

6

This isn't really hard to do: isset is the method you need.

if (!isset($_GET['category'])) {
    // category isn't set
} elseif ($_GET['category'] === '0') {
    // category is set to 0
} else {
    // category is set to something other than 0
}

Note that I have compared for exact equality to the string '0', because GET and POST variables are always strings (or occasionally arrays) and never numbers when PHP first receives them.

edited Oct 04 '11 at 12:28

answered Oct 04 '11 at 11:46

lonesomeday

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Disagree with "always strings". Personally more often than not seen sanitizing in combination with type casting even before validation starts, so that $_GET/$_POST contains `int`, `float`, etc. – Jürgen Thelen Oct 04 '11 at 11:57
@JürgenThelen That's quite unlikely given that we haven't even established that they exist yet... – lonesomeday Oct 04 '11 at 11:59
in this specific case, yes. I'm just disagreeing with trivializing to "GET and POST variables are always strings" for each and every case. – Jürgen Thelen Oct 04 '11 at 12:20
@JürgenThelen Fair enough: clarified. – lonesomeday Oct 04 '11 at 12:28

score 0 · Answer 2 · answered Oct 04 '11 at 11:44

if (!isset($_GET['category']))
{
    1. Do something if $_GET['category'] does not exist at all
}
elseif ($_GET['category'] == 0)
{
    2. Do something if $_GET['category'] == 0
}
elseif (isset($_GET['category']) && ($_GET['category'] != 0)
{
    3. Do something if $_GET['category'] == something other than "does not exist" and 0.
}

My brackets might be slightly out somewhere but hopefully that should help you out.

score 0 · Answer 3 · answered Oct 04 '11 at 11:44

0

There is the filter_input-function for such cases.

answered Oct 04 '11 at 11:44

Lukas Knuth

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score 0 · Answer 4 · edited Aug 01 '12 at 20:20

0

Try this:

if (!isset($_GET['category'])) { // if variable not specified
}
elseif ($_GET['category'] == 0) { // variable is specified and zero
}
else { // variable is specified and not zero
}

edited Aug 01 '12 at 20:20

Wug

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answered Oct 04 '11 at 11:46

Jürgen Thelen

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score 0 · Answer 5 · answered Oct 04 '11 at 11:48

<?php

$bad_values = array(null, '', 'dirty word');

if(isset($_GET['xd']))
{
    if(in_array($_GET['xd'], $bad_values, true))
    {
        // bad, it was null, empty or something else you think is not ok 
    }
    else
    {
        // it's fine, now check whether you got the zero. do a string comparison 

        if($_GET['xd'] == '0')
        {
            // you got the zero, yell at the user
        }
        else
        {
            // you got something else, it might be fine, it might be spoofed. use referential integrity to enforce data integrity in your db
        }
    }
}
else
{
    // it wasn't even sent in the request, that falls under 1)
}

score 0 · Answer 6 · answered Oct 04 '11 at 11:49

Make sure the name attribute of the element that is doing get on the previous page is set, preferably to the same as its id. Then:

$category='';
if ( !isset( $_GET['category'] ) ){
    //1
} else {
    $category=$_GET['category'];
    //3
  if($category==0){
    //2
   }
}

Getting confused with empty, isset, !empty, !isset

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