Will isset() return false if I assign NULL to a variable?

Question

I mean... I "set" it to NULL. So isset($somethingNULL) == true?

Solution 1

bool isset ( mixed $var [, mixed $var [, $... ]] )

Determine if a variable is set and is not NULL.

If a variable has been unset with unset(), it will no longer be set. isset() will return FALSE if testing a variable that has been set to NULL. Also note that a NULL byte ("\0") is not equivalent to the PHP NULL constant.

Return values

Returns TRUE if var exists and has value other than NULL, FALSE otherwise.

From the manual. Examples on the same page.

Solution 2

Yes - from the ISSET() documentation:

$foo = NULL;
var_dump(isset($foo));   // FALSE

/* Array example */
$a = array ('test' => 1, 'hello' => NULL);

var_dump(isset($a['test']));            // TRUE
var_dump(isset($a['foo']));             // FALSE
var_dump(isset($a['hello']));           // FALSE

Comments

[Flatlin3]

why haven't you tried it yourself?

[user229044]

Would have taken less time to test than to ask the question. You even typed the code needed to test your question into the question itself.

[Gregory Pakosz]

now you know you have to search php.net/manual for php reference documentation related questions :)

[openfrog]

I just love you all, that's why I come here for every reason I can find ;)

[user985366]

It took me less time to find this question and answer than it would have taken to figure out test cases, write code, and run it, and still not be sure if I had covered all cases.

[htafoya]

@Flatlin3 because it can then help others that have the same question.

[reformed]

@Flatlin3 what's wrong with documenting the answer?

[Gregory Pakosz]

Rather copy pasting the doc as I did :D But we're doing it to avoid just putting a link in case it gives a 404 afterwards (unlikely to happen with php.net though)

[Tomáš Zato]

So how can I check for array key existence? Prior to finding this question, I thought isset returns true for null variables/keys.

[Rob]

@TomášZato Use array_key_exists() instead.

[Coanda]

A similar function exists for objects: property_exists()