Multiplication Assignment

The *= operator is a combined multiplication assignment operator in PHP. It multiplies the current value of the left operand by the evaluated result of the right operand, and immediately assigns the resulting product back to the left operand.

$variable *= expression;

This syntax is semantically identical to the expanded assignment operation:

$variable = $variable * expression;

Technical Mechanics

Operand Requirements The left operand must be a valid variable reference (an l-value). The right operand can be any literal, variable, or complex expression that evaluates to a scalar value. Because assignment operators have right-to-left associativity and very low precedence, the entire right-hand expression is evaluated before the multiplication occurs.

$a = 2;
$a *= 3 + 4; // Evaluates as $a = 2 * (3 + 4). $a becomes 14.

Type Resolution The data type of the mutated left operand is determined dynamically based on the operands involved in the multiplication:

• Integer (int): Returned if both operands evaluate to integers and the resulting product does not exceed the platform’s maximum integer limit (PHP_INT_MAX).
• Floating-point (float): Returned if either operand is a float, or if the product of two integers results in an integer overflow.

$val = 5;       // int
$val *= 2;      // int(10)
$val *= 1.5;    // float(15.0)

Type Coercion (Type Juggling) If the operands are not strictly numeric, PHP’s engine will attempt to coerce them into numbers before applying the operator:

• Numeric Strings: Strings containing valid numeric formats (e.g., "5", "2.5", "1e3") are automatically cast to int or float.
• Booleans: true is cast to 1, and false is cast to 0.
• Null: null is cast to 0.
• Non-numeric Strings: In PHP 8.0 and later, attempting to multiply by a non-numeric string (e.g., "apple") throws a TypeError.

$x = 10;
$x *= "3";    // $x becomes 30 (int)

$y = 5;
$y *= true;   // $y becomes 5 (int)

$z = 8;
$z *= null;   // $z becomes 0 (int)

Return Value

Like all assignment operators in PHP, *= evaluates to the assigned value. This allows it to be chained or embedded within larger expressions, though this practice is generally discouraged for readability.

$a = 2;
$b = ($a *= 5); // $a becomes 10, and $b is assigned 10

Master PHP with Deep Grasping Methodology!

Learn More