Now that we know how to create variables, let's look at doing some math.
```php
<?php

$a = 1;
$b = 2;
```

To add two values, use the plus symbol.
```php
echo $a + $b;
```

To subtract, use the minus symbol.
```php
echo $b - $a;
```

To multiply two values, use an asterisk.
```php
echo $a * $b;
```

To divide values, use a forward slash.
```php
echo $b / $a;
```

PHP uses the percent symbol for calculating the modulus of two numbers.
The modulus is calculated by dividing two numbers and returning the remainder of the result.
In this example, the value of $mod will be 0.
```php
$mod = 10 % 5;
```

You can also use double asterisks to calculate a number to the power of another number.
The following statement will print 25.
```php
echo 5 ** 2;
```