is_long
Actually, since a wrapper is going to be written, you can check for your own version null values...if you want to be creative for some reason.
<?php
function isnull($data)
{
/** only if you need this
if (is_string($data)) {
$data = strtolower($data);
}
*/
switch ($data) {
// Add whatever your definition of null is
// This is just an example
//-----------------------------
case 'unknown': // continue
case 'undefined': // continue
//-----------------------------
case 'null': // continue
case 'NULL': // continue
case NULL:
return true;
}
// return false by default
return false;
}
?>
is_null
(PHP 4 >= 4.0.4, PHP 5)
is_null —
Finds whether a variable is NULL
Parameters
-
var -
The variable being evaluated.
Return Values
Returns TRUE if var is null, FALSE
otherwise.
Examples
Example #1 is_null() example
<?php
error_reporting(E_ALL);
$foo = NULL;
var_dump(is_null($inexistent), is_null($foo));
?>
Notice: Undefined variable: inexistent in ... bool(true) bool(true)
See Also
- The
NULLtype - isset() - Determine if a variable is set and is not NULL
- is_bool() - Finds out whether a variable is a boolean
- is_numeric() - Finds whether a variable is a number or a numeric string
- is_float() - Finds whether the type of a variable is float
- is_int() - Find whether the type of a variable is integer
- is_string() - Find whether the type of a variable is string
- is_object() - Finds whether a variable is an object
- is_array() - Finds whether a variable is an array
add a note
User Contributed Notes
is_null - [11 notes]
powderz at gmail dot com ¶
6 years ago
strrev xc.noxeh@ellij ¶
5 years ago
$var===NULL is much faster than is_null($var) (with the same result)
I did some benchmarking with 10 million iterations:
$a=null;
isset($a); Took: 1.71841216087s
$a==NULL; Took: 1.27205181122s
$a===NULL; Took: 1.2424390316s
is_null($a); Took: 3.70693397522s
$a=5;
isset($a); Took: 1.15165400505s
$a==NULL; Took: 1.41901302338s
$a===NULL; Took: 1.21655392647s
is_null($a); Took: 3.78501200676s
error_reporting(E_ALL&~E_NOTICE);
unset($a);
isset($a); Took: 1.51441502571s
$a==NULL; Took: 16.5414860249s
$a===NULL; Took: 16.1273870468s
is_null($a); Took: 23.1918480396s
Please note, that isset is only included because it gives a good performance in any case; HOWEVER isset is NOT the same, or the opposite.
But you might be able to use isset() instead of null-checking.
You should not use is_null, except when you need a callback-function, or for conformity with is_int, is_float, etc.
george at fauxpanels dot com ¶
4 years ago
See how php parses different values. $var is the variable.
$var = NULL "" 0 "0" 1
strlen($var) = 0 0 1 1 1
is_null($var) = TRUE FALSE FALSE FALSE FALSE
$var == "" = TRUE TRUE TRUE FALSE FALSE
!$var = TRUE TRUE TRUE TRUE FALSE
!is_null($var) = FALSE TRUE TRUE TRUE TRUE
$var != "" = FALSE FALSE FALSE TRUE TRUE
$var = FALSE FALSE FALSE FALSE TRUE
Peace!
michael at cannonbose dot com ¶
9 years ago
Regarding avoidance of NULLs in your MySQL queries, why not use IS NULL and IS NOT NULL in your WHERE clauses.
SELECT *
FROM someDatabase
WHERE someAttribute IS NOT NULL
Cheers,
Michael
normadize (a) gmail (d) com ¶
11 months ago
Using === NULL instead of is_null(), is actually useful in loaded server scenarios where you have hundreds or thousands of requests per second. Saving microseconds on a lot of "simple" operations in the entire PHP execution chain usually results in being able to serve more pages per second at the same speed, or lowering your cpu usage. People usually write very bad and slow code.
Malfist ¶
5 years ago
Micro optimization isn't worth it.
You had to do it ten million times to notice a difference, a little more than 2 seconds
$a===NULL; Took: 1.2424390316s
is_null($a); Took: 3.70693397522s
difference = 2.46449494362
difference/10,000,000 = 0.000000246449494362
The execution time difference between ===NULL and is_null is less than 250 nanoseconds. Go optimize something that matters.
ai dot unstmann at combase dot de ¶
5 years ago
For what I realized is that is_null($var) returns exactly the opposite of isset($var) , except that is_null($var) throws a notice if $var hasn't been set yet.
the following will prove that:
<?php
$quirks = array(null, true, false, 0, 1, '', "\0", "unset");
foreach($quirks as $var) {
if ($var === "unset") unset($var);
echo is_null($var) ? 1 : 0;
echo isset($var) ? 1 : 0;
echo "\n";
}
?>
this will print out something like:
10 // null
01 // true
01 // false
01 // 0
01 // 1
01 // ''
01 // "\0"
Notice: Undefined variable: var in /srv/www/htdocs/sandbox/null/nulltest.php on line 8
10 // (unset)
For the major quirky types/values is_null($var) obviously always returns the opposite of isset($var), and the notice clearly points out the faulty line with the is_null() statement. You might want to examine the return value of those functions in detail, but since both are specified to return boolean types there should be no doubt.
A second look into the PHP specs tells that is_null() checks whether a value is null or not. So, you may pass any VALUE to it, eg. the result of a function.
isset() on the other hand is supposed to check for a VARIABLE's existence, which makes it a language construct rather than a function. Its sole porpuse lies in that checking. Passing anything else will result in an error.
Knowing that, allows us to draw the following unlikely conclusion:
isset() as a language construct is way faster, more reliable and powerful than is_null() and should be prefered over is_null(), except for when you're directly passing a function's result, which is considered bad programming practice anyways.
claude dot pache at gmail dot com ¶
4 years ago
A small but important difference between "is_null" and "isset" is the following: "is_null" tests if an *expression* (not a *variable*) is null, while "isset" tests if a *variable* has null value or is undefined. The difference is manifested in the two following experiments:
Experiment 1:
<?php
function test() { return null; }
var_dump(is_null(test())); // displays "true"
var_dump(isset(test())); // parse error, because "test()" is not a variable
?>
Experiment 2:
<?php
error_reporting(E_ALL);
var_dump(isset($an_undefined_variable)); // displays "false" since "$an_undefined_variable" is not defined
var_dump(is_null($an_undefined_variable)); // displays "true" (as expected), but throws a notice because "$an_undefined_variable" is not defined.
?>
uioreanu at hotmail dot com ¶
12 years ago
Don't try to test
if ($intSomething==NULL) {
...
}
use is_null() instead.
The first statement misses 0 values.
Regards,
Calin
[Ed. note: this is because == tests for equivalence of value, but not type. NULL evaluates to
false, as does 0, so NULL == 0 is true--even though 0 is type int and NULL is type null.
You should use either is_null() as noted or ===, which returns true only if its operands are
equal and of the same type.]
mdufour at gmail dot com ¶
4 years ago
Testing for a NULL field/column returned by a mySQL query.
Say you want to check if field/column “foo” from a given row of the table “bar” when returned by a mySQL query is null.
You just use the “is_null()” function:
[connect…]
$qResult=mysql_query("Select foo from bar;");
while ($qValues=mysql_fetch_assoc($qResult))
if (is_null($qValues["foo"]))
echo "No foo data!";
else
echo "Foo data=".$qValues["foo"];
[…]
MARSIK ¶
7 years ago
I've tested different values in order to compare 'em with NULL with the help of different operators...
<?php
$arr=array(0, 0.0, '0', '0.0', '',FALSE,'false',NULL, 'NULL');
for ($i=0; $i<count($arr); $i++)
$arr[$i]=array(
$arr[$i],
((integer)($arr[$i]==NULL))
.((integer)($arr[$i]===NULL))
.((integer)is_null($arr[$i]))
);
var_dump($arr);
?>
it gave the following results:
0 : ==NULL
0.0 : ==NULL
'0' : nothing worked =)
'0.0' : nothing...
'' : ==NULL
FALSE : ==NULL
'false' : nothing
NULL : ==NULL, ===NULL, is_null()
'NULL' : nothing
enjoy =)