math operators in PHP
| Operator | Description |
| + | The addition operator |
| - | The subtraction operator , can also be used for negation like this -9 |
| * | The multiplication operator |
| / | the division operator |
| % | the modulus operator , returns the remainder after division . For example 25 % 3 would give us 1 . |
Here is an example
<?php
$number1 = 9;
$number2 = 4;
echo $number1 + $number2;
?>
Which produces the following
13
Incrementing
To increment a variable in PHP we do the following
$yearsindebt++;
This increments the $yearsindebt variable by one , we can also do the following .
$mybill += 20;
which is the same as saying $mybill = $mybill + 20;
Order Of Precedence
The math operators all have to obey an order of precedence which is used in mathematics . This often catches out beginners . Lets look at an example
$calc = 25 + 4 * 2;
What do you think the value of $calc is , well you could add 25 + 4 and get 29 then multiply by 2 and get 58 . Wrong . The rules of precedence say that multiplication gets calculated before addition so you get 4 * 2 is 8 and then 25 + 8 = 33 . 33 is the correct answer . A big difference from 58 .
At school I was taught to use BODMAS to help remember order of precedence this is basically Brackets , Division , Multiplication , Addition , Subtraction. What if you want to add the 25 + 4 first and then multiply this by 2 , well you can do the following.
$calc = (25 + 4) * 2;
Now the brackets get evaluated first because they come before multiplication in the order of precedence..