分配運算子

簡單算術：

$var = 1      # Assignment. Sets the value of a variable to the specified value
$var += 2     # Addition. Increases the value of a variable by the specified value
$var -= 1     # Subtraction. Decreases the value of a variable by the specified value
$var *= 2     # Multiplication. Multiplies the value of a variable by the specified value
$var /= 2     # Division. Divides the value of a variable by the specified value
$var %= 2     # Modulus. Divides the value of a variable by the specified value and then
              # assigns the remainder (modulus) to the variable

增量和減量：

$var++   # Increases the value of a variable, assignable property, or array element by 1
$var--   # Decreases the value of a variable, assignable property, or array element by 1