How do I check if a $_GET parameter exists but has no value?

Question

I want to check if the app parameter exists in the URL, but has no value.

Example:

my_url.php?app

I tried isset() and empty(), but don’t work. I’ve seen it done before and I forgot how.

score 34 · Accepted Answer · answered Sep 19 '12 at 21:57

34

Empty is correct. You want to use both is set and empty together

if(isset($_GET['app']) && !empty($_GET['app'])){
    echo "App = ".$_GET['app'];
} else {
    echo "App is empty";
}

answered Sep 19 '12 at 21:57

Jay Hewitt

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Your "App is empty" will display if it's not set in the first place, I'd put an elseif statement in there – Scuzzy Sep 19 '12 at 22:28
5

Indeed, a more accurate statement would be: if(isset($_GET['app']) && !empty($_GET['app'])){ echo "App = ".$_GET['app']; } elseif(isset($_GET['app'])) { echo "App is empty"; } else { echo "App is not set"; } – Jay Hewitt Sep 20 '12 at 13:00

score 5 · Answer 2 · answered Sep 19 '12 at 21:49

empty should be working (if(empty($_GET[var]))...) as it checks the following:

The following things are considered to be empty:

"" (an empty string)
0 (0 as an integer)
0.0 (0 as a float)
"0" (0 as a string)
NULL
FALSE
array() (an empty array)
$var; (a variable declared, but without a value)

Here are your alternatives:

is_null - Finds whether a variable is NULL

if(is_null($_GET[var])) ...

defined - Checks whether a given named constant exists

if(defined($_GET[var])) ...

If your parameter is an integer that can be zero, then empty fails if its value is zero. — Mehmed, Sep 20 '19 at 16:40

score 2 · Answer 3 · edited Sep 19 '12 at 21:51

2

if( isset($_GET['app']) && $_GET['app'] == "")
{

}

edited Sep 19 '12 at 21:51

sachleen

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answered Sep 19 '12 at 21:49

84em

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2

score 2 · Answer 4 · answered Oct 30 '17 at 17:38

2

You can simply check that by array_key_exists('param', $_GET);.

Imagine this is your URL: http://example.com/file.php?param. It has the param query parameter, but it has not value. So its value would be null actually.

array_key_exists('param', $_GET); returns true if param exists; returns false if it doesn't exist at all.

answered Oct 30 '17 at 17:38

Ali

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`http://example.com/file.php?param` actually results in `isset($_GET['param'])` returning true! – Keldon Alleyne Mar 13 '18 at 18:46
This is an actual answer to the question. Thank you, Ali – Bjørn H. Sandvik Mar 01 '20 at 18:50

How do I check if a $_GET parameter exists but has no value?

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