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PHP is_null() Function

Quick summary: The PHP is_null() function checks whether a variable is null.

PHP is_null() Syntax 

is_null(mixed $value): bool
PHP

PHP is_null() Basic examples 

$a = null;
var_dump(is_null($a));
PHP
Output:
bool(true)

Returns true if the variable is null.

var_dump(is_null(0));
PHP
Output:
bool(false)

Zero is not null.

PHP is_null() Real-world usage 

$value = null;
if (is_null($value)) {
    echo 'Value missing';
}
PHP
Output:
Value missing

Explicitly checks for missing values.

PHP is_null() Edge cases 

var_dump(is_null(undefined_variable));
PHP
Output:
Notice: Undefined variable

The variable must exist to be checked safely.

PHP is_null() Common mistakes

Using is_null instead of strict comparison

is_null is equivalent to === null.

Incorrect
is_null($a);
Correct
$a === null;

Strict comparison is often clearer.

PHP is_null() Frequently Asked Questions

What does is_null() do?

Checks if a variable is null.

Use case?

Validating optional values.

Return type?

bool.

Common mistake?

Confusing with empty().

Alternative?

$var === null.

Strict check?

Yes.

Handles undefined?

No.

Performance?

Very fast.

Safe?

Yes.

Used in validation?

Yes.

Works with objects?

Yes.

Best practice?

Use strict comparison.

PHP is_null() Related PHP Functions