> ## Documentation Index
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> Use this file to discover all available pages before exploring further.
# PHP Exponentiation
The `**` operator is the arithmetic exponentiation operator in PHP, used to raise a base operand to the power of an exponent operand. Introduced in PHP 5.6, it serves as the native syntactic equivalent to the `pow()` function.
## Syntax
```php theme={"dark"}
$result = $base ** $exponent;
```
## Associativity
Unlike most mathematical operators in PHP which are left-associative, the `**` operator is **right-associative**. When multiple exponentiation operators are chained in a single expression, the evaluation engine processes them from right to left.
```php theme={"dark"}
$result = 2 ** 3 ** 2;
// Evaluated as: 2 ** (3 ** 2) -> 2 ** 9 -> 512
// NOT evaluated as: (2 ** 3) ** 2 -> 8 ** 2 -> 64
```
## Precedence
The `**` operator has a higher operator precedence than standard multiplicative (`*`, `/`, `%`) and additive (`+`, `-`) operators.
Crucially, it also has a higher precedence than the unary negation operator (`-`). If you intend to raise a negative number to a power, the base must be explicitly wrapped in parentheses.
```php theme={"dark"}
$a = -2 ** 2; // Evaluated as -(2 ** 2) -> -4
$b = (-2) ** 2; // Evaluated as (-2) ** 2 -> 4
```
## Type Resolution and Coercion
The return type of the `**` operator is dynamically resolved by the Zend Engine based on the operands and the mathematical result:
* **`int`**: Returned if both operands are integers, the exponent is greater than or equal to zero, and the resulting value does not exceed `PHP_INT_MAX` (integer overflow).
* **`float`**: Returned if either operand is a float, if the exponent is negative (which mathematically yields a fraction), or if the calculated result exceeds the maximum integer bounds.
```php theme={"dark"}
var_dump(2 ** 3); // int(8)
var_dump(2 ** -1); // float(0.5)
var_dump(2.0 ** 3); // float(8)
```
## Compound Assignment
PHP provides a corresponding compound assignment operator (`**=`) to mutate a variable in place by raising its current value to the power of the right-hand operand.
```php theme={"dark"}
$base = 4;
$base **= 2; // Equivalent to: $base = $base ** 2;
// $base is now int(16)
```
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