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# PHP Modulo Assignment
The `%=` (modulo assignment) operator is a combined arithmetic-assignment operator that divides the variable on the left operand by the expression on the right operand, and assigns the integer remainder of that division back to the left operand.
## Syntax
```php theme={"dark"}
$variable %= expression;
```
This is functionally equivalent to the expanded assignment form:
```php theme={"dark"}
$variable = $variable % expression;
```
## Technical Mechanics
* **Implicit Integer Casting:** Before the modulo operation is executed, PHP strips the fractional parts of both operands, implicitly coercing them into integers. For example, `5.9 %= 2.8` is evaluated strictly as `5 % 2`.
* **Signage:** The sign of the resulting remainder is determined exclusively by the dividend (the left operand). The sign of the divisor (the right operand) is ignored during evaluation.
* **Floating-Point Limitation:** Because the `%=` operator forces integer coercion, it cannot be used to find the remainder of floating-point divisions. Developers must use the `fmod()` function for floating-point modulo operations.
* **Exceptions:** If the right operand evaluates to `0`, PHP 8.0 and later will throw a `DivisionByZeroError` exception.
## Evaluation Examples
```php theme={"dark"}
// Standard integer evaluation
$a = 10;
$a %= 3;
// Evaluates as: 10 % 3. $a becomes 1.
// Implicit float-to-integer coercion
$b = 10.8;
$b %= 3.9;
// Evaluates as: 10 % 3. $b becomes 1.
// Negative dividend (result takes the sign of the left operand)
$c = -10;
$c %= 3;
// Evaluates as: -10 % 3. $c becomes -1.
// Negative divisor (sign of the right operand is ignored)
$d = 10;
$d %= -3;
// Evaluates as: 10 % -3. $d becomes 1.
```
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