creating functions .. help

Anon

I am a little new at PHP, and I have read the PHP manual and pretty much understood what I needed to know.
Now I'm trying to make functions to ease the process of building a site.
But I have not understood how a function is build.
To take the example from the PHP manual:

function foo ($arg_1, $arg_2, ..., $arg_n) {
echo "Example function.\n";
return $retval;
}

so far i've understood that foo is the name of the function, and when I want to "execute" the function i use foo();
What I so far don't understand is, is it required to set $arg_1 .... ?, and if it is what are their purpose ?
also the return $retval; .. what is the use for that ?

Put shortly:

Can someone walk me through the creation of a function, perhaps give an example.

Thanks

Brian Schmidt

Anon

Well a function performs an operation of sorts on a given argument or on internal arguments

//A reall simple example and useless example
function foo() {
print "Hello World";
}
//Sample Usage
foo();
//This would result in
Hello World

//Or you could pass an argument like so
function foo($string) {
print $string;
}
//Sample Usage
foo("Hello World");
//This would result in
Hello World

//Or you could retrun the value
function foo($string) {
$string = $string." Fool";
return $string;
}
//Sample Usage
print foo("Hello World");
//This would result in
Hello World Fool

//Or you could test a variable
function check_name($name) {
if (strlen($name) > 5) {
return 1;
}
}

if (check_name("Billyb")) {
print "Name Okay";
}
else {
print "Name must be at least 5 characters long";
}

Anon

I'll start from the begining. To create a function you would use the following format

function <function name> (<arguments if any>)
{
//function code
}
an example for that would be function that takes in 2 numbers, adds them, and returns an answer

function add_num($num1, $num2)
{
$answer = ($num1+$num2);
return $answer;
}
This function will take in 2 numbers (num1,num2) add them together and store the answer in a variable named $answer. The function will than return (eg. make the variable avail.) to the actual code by the return statement. To call this function you would do

add_num(x,y);
Here's a complete example:

//begin here
function add_num($num1, $num2)
{
$answer = ($num1+$num2);
return $answer;
}

$ans = add_num(4,6); //assign the return value to $ans
print "$ans"; //print the value of ans. In this case 10 since 4+6 is 10.