Script 3.10 & Functions In General

[Paul]

Hiya,

Referring to script 3.10 it appears that a function needs to be either returned or printed. I'm struggling to understand why that is.

 

In the above mentioned script the function calculate_total performs the calculation of the total and puts it in a variable called $total.

 

Further down the script the function is called based on the values entered on the form and the result placed in a variable called $sum. Now, from the 'Variable Scope' article at the end of the chapter a defined variable within a function cannot be accessed outside it. This, I assume, is why the results of the calculation are put into $sum and not $total.

 

However why does the function need to have the line - return number_format ($total, 2) ?

 

In my mind the function defines the job, this job is then called further down the script and it's results stored in $sum. Why is the return line needed?

 

Thanks

Paul

[Jonathon]

Hi Paul,

 

I havent looked at the script but the your passing the variables into that function from the form. (from memory). The function tidies up the code and calculations and the number_format formats the the answer to a 2 decimal place because it's meant to return the answer as a monetary value i.e. $4.67, not $4.675636224...., various calculations will rarely return a figure exactly in 2 decimal format hence the use of this function.

[Larry]

Hello Paul,

 

You need to get the value out of the function somehow. A function is a "black box": the code outside of the script can't see into it. So the function's return line is how the function returns a value. When the function is called, the returned value is assigned to $sum.

 

Does that answer your question?