The ($arg) function

busman posted this at 15:57 — 16th February 2009.

Joined: Dec 2008

<?php
 
    function show_number($num){
     $new_number = make_double($num);
     echo( "The value is $new_number" );
    }
    function make_double($arg){
     return $arg + $arg;
    }
?>

PHP Function

<?php
 show_number(12); 
?>

Could some one please explain this code to in very simple terms. It does work but I would like to make perfect sense of it. The make_double($arg)is diffrent to in the show_number($num) function it is make_double($num). Why?

Thanks

decibel.places posted this at 16:22 — 16th February 2009.

He has: 1,494 posts

Joined: Jun 2008

hi busman,

the code calls the show_number() function and passes the value 12 to it

show_number(12);

the function assigns the passed value 12 to the variable $num

function show_number($num)

then it passes the value of $num which is 12 to the function make_double() and assigns the returned value (24) to a variable $new_number

$new_number = make_double($num);

the make_double() function adds $arg + $arg to double its value - the value of $arg is the value of $num which is 12 - and returns the sum (24) to the show_number() function as the value of $new_number

function make_double($arg){
     return $arg + $arg;
}

function show_number() continues by echoing (or writing) the text plus the value of $newnumber that was returned by function make_double() - ie 24

echo( "The value is $new_number" );

however, I would remove the parentheses from the echo statement:

echo "The value is $new_number";

on the page you should see

The value is 24

I would rewrite the show_number() function - the make_double() function is unnecessary:

<?php
    function show_number($num){
     $new_number = $num + $num;
     echo "The value is $new_number";
    }
?>

busman posted this at 16:36 — 16th February 2009.

They have: 20 posts

Joined: Dec 2008

Thank you for all your help. I agree with your method, it make more sence and it is much more practical.

Thanks

greg posted this at 16:50 — 16th February 2009.

He has: 1,581 posts

Joined: Nov 2005

EDIT: decibel beat me to it (although I mentioned not using a function at all, which is fine (better) in most cases)

I don't have a fantastic knowledge with functions, so perhaps someone else will explain why some of that code is "required", but to me it appears to be extremely bloated.

To double a number, wouldn't this be better:

<?php
   
function double_number($num){
     $num = $num * 2;
     return $num;
}

echo double_number(12);
?>

Or instead of echoing you can add the value to a var

<?php
$doubled_number = double_number(12);
?>

Then echo it in whatever text you want

<?php
echo "My new number now doubled is ".$doubled_number;
?>

But to be honest, I don't see the point in ever using a function for something so simple unless you use it many times, which is the point of a function.

Simply having this would suffice in "most" cases and is much less use of resource for the server:

<?php
echo "My new number is "; echo 12 * 2;
?>

The only time you would really use the above in a function is if you are doubling many numbers throughout your page/script/site, and even then only if there were other calculations, such as Round, Ceil or Floor