CODEWITHSUNDEEP
php
Brian
Brian

Reputation: 45

if statement evaluates to true on NULL variable when using is_null()

So I've got a form with a modal, that modal has 3 rows with 2 text fields each, if the user (me in this prod case) fills out only 2 rows, and leave the other row empty, that 3rd value should be NULL.

In my script I've got:

if (!is_null($_POST['packageDependencies']['bundle'][2])) {
$packageDependency3 = $_POST['packageDependencies']['bundle'][2] . "|" . $_POST['packageDependencies']['version'][2] . "|" . $_POST['packageDependencies']['repository'][2];
$depends = "<key>dependencies</key>
            <array>
                <string>$packageDependency1</string>
                <string>$packageDependency2</string>
                <string>$packageDependency3</string>
            </array>
            ";

}

So I'm checking if (!is_null($3rdRow)) { //Do this }, but the variable $_POST['packageDependencies']['bundle'][2] is in fact NULL, as I use var_dump($_POST['packageDependencies']['bundle'][2]); and I get NULL printed to the page, but the if statement is still processing as if it isn't NULL.

$depends gets fwrite() to an XML file, and when I open it, I only see || and but that shouldn't be there as the variable is NULL as I entered no values into those input fields.

Upvotes: 1

Views: 39

Answers (2)

Brian
Brian

Reputation: 45

Even though !empty() did the trick, I've decided to use == to be less ambiguous. The answers found here are quite intuitive.

EDIT: As per @gview, adding (!empty(trim($var))) is the best bet as if a user accidentally presses the space key after a tab, it will avoid any errors.

Upvotes: 0

gview
gview

Reputation: 15361

Given my advice, a more complete solution would be:

if (!empty(trim($_POST['packageDependencies']['bundle'][2]))) {

NULL is a specific state of a variable that involves the way PHP associates the name of a variable with a variable location. You can think of it like a flag, that indicates a variable name exists, but there is no storage location associated with it. There are a number of situations that empty with trim will catch that will bypass a check against null.

Upvotes: 1

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