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# PHP null
`null` is a special unit type in PHP representing a variable with no value. It is the sole possible value of the `null` data type, indicating the intentional absence of any typed data or object reference.
The `null` constant is case-insensitive, though lowercase `null` is the accepted standard per PSR-12 guidelines.
```php theme={"dark"}
$emptyVariable = null;
$alsoEmpty = NULL; // Valid, but not recommended
```
A variable is internally evaluated as `null` under three specific conditions:
1. It has been explicitly assigned the constant `null`.
2. It has been declared but not yet initialized with any value.
3. It has been explicitly destroyed using the `unset()` language construct.
## Type Checking and Comparison
Because PHP is a loosely typed language, evaluating `null` requires strict comparison to avoid unintended type juggling.
```php theme={"dark"}
$var = null;
// Strict comparison (Recommended)
// Evaluates to true ONLY if $var is exactly null
$var === null;
// Built-in type checking function
// Functionally identical to strict comparison
is_null($var);
// Loose comparison (Not recommended for null checks)
// Evaluates to true for null, false, 0, 0.0, "", and []
$var == null;
```
## Type Coercion
When a `null` value is cast or coerced into other scalar or compound types, PHP resolves the absence of value into the empty equivalent of the target type:
```php theme={"dark"}
$var = null;
$asBool = (bool) $var; // Evaluates to: false
$asInt = (int) $var; // Evaluates to: 0
$asFloat = (float) $var; // Evaluates to: 0.0
$asString = (string) $var; // Evaluates to: "" (empty string)
$asArray = (array) $var; // Evaluates to: [] (empty array)
```
## Null-Specific Operators
PHP provides specific operators designed to handle `null` evaluation natively at the syntax level.
**Null Coalescing Operator (`??`)**
Evaluates the left operand. If it is strictly not `null` and exists, it returns it; otherwise, it returns the right operand.
```php theme={"dark"}
$value = $uninitializedVar ?? 'fallback';
```
**Null Coalescing Assignment Operator (`??=`)**
Assigns the right operand to the left operand only if the left operand is currently `null`.
```php theme={"dark"}
$var ??= 'assigned_because_null';
```
**Nullsafe Operator (`?->`)**
Allows property or method access on an object that might be `null`. If the object evaluates to `null`, the entire chain short-circuits and returns `null` without throwing a fatal error.
```php theme={"dark"}
// PHP 8.0+
$result = $object?->method();
```
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