php Ternary Operator failing when a 0 is entered

Question

The following code works great until inQuantity receives a zero "0". Upon receiving a zero it evaluates it as empty and puts in a null instead of a "0". If "0.00" is entered it is evaluated as not empty.

$_POST['inQuantity'] = (!empty($_POST['inQuantity'])) ? $_POST['inQuantity'] : NULL;

the following code produces the same result

    if (empty($_POST['inQuantity'])) {
        $state = "empty";
    } else {
        $state = "full";
    }

when inQuantity is "0" the output of $state is "empty"

Anybody know why this is?

This is not a "failure" at all, it is simply how php (and most other languages) interpret a '0' value. It is well documented behaviour. You probably want this as condition instead: `(isset($_POST['inQuantity']))` — arkascha, Apr 04 '14 at 06:12
Note that the mentioned duplicate speaks of any variable, whereas this is about values taken from GPC; the difference is that the unwanted `empty()` behaviour is limited to only `"0"`. — Ja͢ck, Apr 04 '14 at 06:21
Thank you very much, newbie here, still seemed like a bug to me. — user2793447, Apr 04 '14 at 06:22
Although it's documented, using `empty()` in this case would be the wrong function to use as well :) — Ja͢ck, Apr 04 '14 at 06:24
I would like to add that the example in the manual "// Example usage for: Ternary Operator $action = (empty($_POST['action'])) ? 'default' : $_POST['action']; " is a poor example for newbies — user2793447, Apr 04 '14 at 06:31

score 5 · Answer 1 · edited Apr 04 '14 at 06:16

5

You should not use empty in this case, because it is standard behaviour of empty to return true in these cases:

"" (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)

Try to use isset():

$_POST['inQuantity'] = (isset($_POST['inQuantity'])) ? (float) $_POST['inQuantity'] : NULL;

edited Apr 04 '14 at 06:16

Ja͢ck

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answered Apr 04 '14 at 06:12

Barif

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Ja͢ck · Answer 2 · 2014-07-16T08:02:13.677

Because empty('0') yields true you would have to be more specific as to what you consider to be empty; for example:

if (isset($_POST['inQuantity'])) {
    // The 'inQuantity' parameter was passed via $_POST
} else {
    // Not passed
}

You could consider an empty string to be, well, empty:

if (isset($_POST['inQuantity']) && strlen($_POST['inQuantity'])) {
    // The 'inQuantity' parameter was passed via $_POST
    // and contains at least one character (worst case, it's an array)
} else {
    // Not passed or empty
}

Another way is to use input filtering:

$quantity = filter_input(INPUT_POST, 'inQuantity', FILTER_VALIDATE_FLOAT, FILTER_NULL_ON_FAILURE);

if ($quantity !== null) {
    // value was passed and is a valid floating point value
}

php Ternary Operator failing when a 0 is entered

2 Answers2