PHP NULL
NULL is a special type that represents a variable with no value.
NULL is a special data type that has only one value: NULL. A variable is NULL if it has been assigned the constant NULL, has not been set, or has been unset with unset().
Use is_null() or isset() to check for it.
Example
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When to use it
- Initialise an optional config value to null before conditionally assigning it from user input.
- Check is_null() on a database query result to determine whether a record was found.
- Set a session variable to null to clear it without calling unset() when resetting state.
More examples
Assigning and checking null
Initialising to null and checking is_null() clearly expresses intent before lazy assignment.
<?php
$token = null;
if (is_null($token)) {
$token = bin2hex(random_bytes(16));
}
echo $token;null with isset and empty
isset() returns false for null variables, making it the right guard for nullable values.
<?php
$user = null;
var_dump(isset($user)); // bool(false)
var_dump(empty($user)); // bool(true)
var_dump(is_null($user)); // bool(true)Nullable type declarations
The ?array return type signals null is a valid return value, which ?? then handles cleanly.
<?php
function findUser(int $id): ?array {
$users = [1 => ["name" => "Alice"]];
return $users[$id] ?? null;
}
$user = findUser(99);
echo $user === null ? "Not found" : $user["name"];
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