One common task when manipulating number variables is to reassign them to their old value with some operation performed on it.
$savings = 800; $bike_cost = 75; $savings = $savings - $bike_cost; echo $savings; // Prints: 725
This is such a common task that PHP provides a shorter syntax using arithmetic assignment operators:
|Operation:||Long Syntax:||Short Syntax:|
|Add||$x = $x + $y||$x += $y|
|Subtract||$x = $x - $y||$x -= $y|
|Multiply||$x = $x * $y||$x *= $y|
|Divide||$x = $x / $y||$x /= $y|
|Mod||$x = $x % $y||$x %= $y|
We could use this shorter syntax to rewrite the above code:
$savings = 800; $bike_cost = 75; $savings -= $bike_cost; echo $savings; // Prints: 725
With mathematical assignment operators, PHP doesn’t allow spaces between the two characters.
Ready for one more shortcut? Increment operators allow us to subtract or add one to a number with just two characters.
$age = 89; $age++; echo $age; // Prints: 90 $days_til_vacation = 7; $days_til_vacation--; echo $days_til_vacation; // Prints: 6
In the code above, we used the post-increment (
++) operator to add one to
$age and we used the post-decrement operator (
--) to subtract one from
Those keystrokes can add up, so let’s practice using arithmetic assignment operators on variables!
We’re going to do a mathematical “magic” trick. Create a variable,
$my_num and assign as its value any number.
Next, create a second variable,
$answer and assign
$my_num as its value.
Use the addition assignment operator to add 2 to
Use the multiplication assignment operator to multiply
$answer by 2.
Use the subtraction assignment operator to subtract 2 from
Use the division assignment operator to divide
$answer by 2.
Almost there. Use the subtraction assignment operator to subtract your original number (
$answer. Finally, use
echo to print
$answer to the terminal.
If everything went as it should,
$answer should be 1. No matter what your original number was! Don’t believe us? Go ahead try it with a different number for the value of