简单的算术：
$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
递增和递减：
$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