Php if not isnull

Php php isnull function code example

Return value: It returns true if the object has null value otherwise it returns false. Passing a number in the _.isNull() function: The _.isNull() function takes the parameter passed to it and then checks whether the object has null value or not.

PHP: is_null() function

Description

The is_null () function is used to test whether a variable is NULL or not.

*Mixed: Mixed indicates that a parameter may accept multiple (but not necessarily all) types.

Return value:

Returns TRUE if var_name is null, FALSE otherwise.

Value Type : Boolean

View the example in the browser

Practice here online:

If condition check if null in php Code Example, xxxxxxxxxx. 1. // The is_null () function checks whether a variable is NULL or not. This function returns true (1) if the variable is NULL, otherwise it returns false/nothing. 2.

Is there an equivalent to Microsoft SQL’s isnull() function in PHP?

In tSQL there’s a great little function called isnull(), which takes the following:

ISNULL ( check_expression , replacement_value ) 

I know about is_null() in PHP, but it’s no the same. Is there another function I’m missing?

I can see it being useful in cases like this one (assume the isnull() here would work the same as tSQL):

die("Function does not exist" . isnull($_POST['function'], ". No function was specified")); 

The closest you could get to an isnull function in PHP would be using isset and the ternary operator:

$val = isset($val) ? $val : $value_if_val_is_null; 

VBScript IsNull Function, The IsNull function returns a Boolean value that indicates whether a specified expression contains no valid data (Null). It returns True if expression is Null; otherwise, it returns False. Syntax. IsNull(expression) Parameter Description; expression: Required. An expression: Example. Example

Underscore.js _.isNull() Function

_.isNull() function:

• It is used to find whether the value of the object is null.
• If object has null value then the output will be true otherwise false.
• We can even perform addition, subtraction etc operations in this function.

Parameters:
It takes only one argument which is the object that needs to be tested.

Return value:
It returns true if the object has null value otherwise it returns false.

1. Passing a number in the _.isNull() function:
The _.isNull() function takes the parameter passed to it and then checks whether the object has null value or not. In this case since the value is a defined number “10”, so the output is not null. Therefore, the output will be false.

HTML

2. Passing “null” to the _.isNull() function:
Since here we have passed “null” so we need not check for the object. We know that the value passed to the _.isNull() function itself has value “null”. Therefore, the output will be true.

HTML

3. Passing undefined” to the _.isNull() function:
The _.isNull() function takes the parameter passed to it which here is “undefined”. We know that if anything is undefined, then it’s value will be null. And hence, the answer is true.

HTML

4. Performing operations on the output of _.isNull() function:
In this first we have directly stored the output of both the above 2 examples (2, 3) in variables a and b, and then we have done an addition operation in both the results. Finally, stored it in the third variable. Since the output of _.isNull() is false when we passed and true when we passed null, therefore false is stored in ‘a’ variable and true is stored in ‘b’ variable. Now if we perform addition (+) operation on both the ‘a’, ‘b’ variables then we will have true as ‘b’ is true. Hence ‘c’ variable will become 1.

Источник

is_null

Finds whether the given variable is null .

Parameters

The variable being evaluated.

Return Values

Returns true if value is null , false otherwise.

Examples

Example #1 is_null() example

$foo = NULL ;
var_dump ( is_null ( $inexistent ), is_null ( $foo ));

Notice: Undefined variable: inexistent in . bool(true) bool(true)

See Also

• The null type
• isset() — Determine if a variable is declared and is different than 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

User Contributed Notes 9 notes

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.

See how php parses different values. $var is the variable.

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

In PHP 7 (phpng), is_null is actually marginally faster than ===, although the performance difference between the two is far smaller.

PHP 5.5.9
is_null — float(2.2381200790405)
=== — float(1.0024659633636)
=== faster by ~100ns per call

PHP 7.0.0-dev (built: May 19 2015 10:16:06)
is_null — float(1.4121870994568)
=== — float(1.4577329158783)
is_null faster by ~5ns per call

A quick test in 2022 on PHP 8.1 confirms there is still no need to micro-optimize NULL checks:

// Comparison Operator
$before = microtime ( true );
$var = null ;
for ( $i = 0 ; $i < 1000000000 ; $i ++) if( $var === null ) <>
>
$after = microtime ( true );
echo ‘ ===: ‘ . ( $after — $before ) . » seconds\n» ;

// Function
$before = microtime ( true );
$var = null ;
for ( $i = 0 ; $i < 1000000000 ; $i ++) if( is_null ( $var )) <>
>
$after = microtime ( true );
echo ‘is_null: ‘ . ( $after — $before ) . » seconds\n» ;

// ===: 4.1487579345703 seconds
// is_null: 4.1316878795624 seconds

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:

$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.

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.

$var===NULL is much faster than is_null($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.

I’ve found that for HTTP requests such as POST, is_null isn’t the most reliable choice for checking if empty.

if(trim($var) == «») // do something
>

I think the request does something to the input that makes it definitely not NULL.

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

Источник

Is a PHP variable NULL or empty?

In this short PHP tutorial, we’re going to check if a variable is null or empty. We’ll first create a function to check for a NULL value, then an empty value, and finally combine both functions for NULL or empty.

In this article

isNull

Let’s start with a basic PHP function to validate whether our variable is NULL . We’ll use isset to check for NULL .

Our isNull function does not return true for empty strings, we’ll have to cater for that also.

isEmpty

Next, we create our isEmpty function.

We simply check for an empty string and return true or false .

isNullOrEmpty

Our final function is a combination of isNull and isEmpty

The function isNullOrEmpty will determine whether a variable is not null or empty.

Key Takeaways

• Our code validates a string variable for null or empty.
• We use a simple if not NULL or empty check to determine whether to return TRUE or FALSE .
• You could update the function to trim the variable before checking for empty.
• Related PHP functions: empty, is_null

This is the footer. If you’re reading this, it means you’ve reached the bottom of the page.
It would also imply that you’re interested in PHP, in which case, you’re in the right place.
We’d love to know what you think, so please do check back in a few days and hopefully the feedback form will be ready.

Источник