Writing a Math Function

[github-learning-lab]

Functions

Functions are pre-built commands in PHP that do some of the hard work for you. You can also write your own custom function. The function we will write will calculate tax, but first let's go over using math in PHP

Using Math

By using math symbols you can add(+), subtract(-), multiply(*) or divide(/) variables. Add this to the bottom of your php tags:

$amount=800;
$taxRate=0.0825;
$addedTax= $amount*$taxRate;  //amount = 800, tax = .0825
echo $addedTax;

Refresh the page, and leave a comment with the value of $addedTax to continue.

[shukla-m]

66

[github-learning-lab]

Alright, 66 was the right answer! Now lets write a function that will calculate tax for our products.

Using Default Functions

There are many pre-built default functions available with php, so you should check to see if one exists before trying to create one. For instance, if we want to round 811.882 to 811.88 we can use the round() function which requires a variable and the number of digits to round to.
For example:

round(811.882,2); // should return 811.88

Create a Function

At the very bottom of the PHP code (but before the ?>), type the following code to create a tax calculating function:

  function tax_calc($amount,$tax){
  	$calculate_tax = $amount*$tax;
  	$amount = round($amount+$calculate_tax,2);
  	return $amount;
  }

When when want to use this function, pass in values for $amount and $tax like so:

echo tax_calc(750,0.223); // When you refresh your page you should the value 917.25 at the bottom of the screen.

When you have successfully defined and called your function, push your changes to GitHub.

git add index.php
git commit -m"add tax calc function"
git push origin master