PHP checking for NULL value

Question

Just out of curiosity (and a bit of necessity):

if(! is_null($var)){
     //do something
}

Is the above statement the same as

if($var != NULL){
//do something
}

Have you tried it? What are your own conclusions? Do you have any specific reason for your suspicions? — Lix
– Lix, Commented Feb 12, 2014 at 15:23
Yes, they are. Look at the php comparision table: php.net/manual/en/types.comparisons.php — ozahorulia
– ozahorulia, Commented Feb 12, 2014 at 15:23
I have, the above statement seems to evaluate to true regardless if the var is NULL or not. Seems to me it shouldnt be this way — Kisaragi
– Kisaragi, Commented Feb 12, 2014 at 15:24
There is a difference though. The last one doesnt use a function, which might have influence on the memory used. But not in an amount you should care about — Martijn
– Martijn, Commented Feb 12, 2014 at 15:26
Might depend on the way it's used. Even though you didn't add a mysql tag, are you using this for DB, or just PHP? — Funk Forty Niner
– Funk Forty Niner, Commented Feb 12, 2014 at 15:29

Ron van der Heijden · Accepted Answer · 2020-10-13 21:02:48Z

4

No they are not the same.

The is_null function compairs the type also.

Example:

var_dump(is_null(0)); // bool(false) 
var_dump(0 == NULL);  // bool(true) 
var_dump(0 === NULL); // bool(false)

So in your case

if(! is_null($var)){
     //do something
}

Would be the same as

if($var !== NULL){
    //do something
}

edited Oct 13, 2020 at 21:02

answered Feb 12, 2014 at 15:29

Ron van der Heijden

15.1k7 gold badges62 silver badges86 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Jesper · Accepted Answer · 2014-02-12 15:33:54Z

1

Yes this is (almost) correct, you can test this yourself:

    $emptyvar1 = null;
    $emptyvar2="";
    if(is_null($emptyvar1) && $emptyvar1 == NULL){
        echo "1";
    }
    if(is_null($emptyvar2)){
        echo "2";
    }
    if($emptyvar2 == null){
        echo "3";
    }
    if($emptyvar2 === null){
        echo "4";
    }

This will print 1 and 3. because an empty string is equal to null if you only use 2 times = if you use 3 times = it aint.

=== also checks object type == only checks value

answered Feb 12, 2014 at 15:33

Jesper

6095 silver badges9 bronze badges

Comments

Tsueah · Accepted Answer · 2014-02-12 15:36:15Z

I'm not sure what exactly you're testing, but on:

a) $var = NULL; neither of the statements triggers,

b) $var = 0; is_null triggers and

c) $var = ''; is_null triggers aswell.

So the statements above are definitely not coming to the same conclusion.

See for yourself:

echo 'testing NULL case<br>';
$var = NULL;
if(! is_null($var)){
    echo 'var is_null<br>';
}
if($var != NULL){
    echo 'var != null<br>';
}

echo 'testing 0 case<br>';
$var = 0;
if(! is_null($var)){
    echo 'var is_null<br>';
}
if($var != NULL){
    echo 'var != null<br>';
}

echo 'testing empty string case<br>';
$var = '';
if(! is_null($var)){
    echo 'var is_null<br>';
}
if($var != NULL){
    echo 'var != null<br>';
}

this outputs

testing NULL case
testing 0 case
var is_null
testing empty string case
var is_null

Collectives™ on Stack Overflow

PHP checking for NULL value

3 Answers 3

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related