Undefined Variables

I took this code, below, from http://www.oxyscripts.com/viewcode.php?id=22. This is just a few lines <?php
function sdie($desc)
{
echo $desc;
exit;
}

Variables $desc. Where is it defined? This may be a beginner question, but as I have been moving into more advanced scripting as my knowledge empowers me, I see more of 'undefined' variables. Could someone tell me if I am wrong, or explain them to me?

Thanks

$desc is a parameter to the function. It gets defined the moment you call the sdie() function, like sdie('hello world'). That's why your sample code hasn't got any undefined variables, everything is normal and ok here.

function sdie($desc)
{
echo $desc;
exit;
}

$desc is defined where shown above

mordred got there first with a much better explanation :)

Mordred,

so when the code goes echo $desc; what does it echo?

Thanks for the help

<?php

function sdie($desc)
{
echo $desc;
exit;
}

sdie('Hello World!'); // prints Hello World!

sdie('!dlroW olleH'); // prints !dlroW olleH

<?php
function sdie($desc)
{
echo $desc;
exit;
}

sdie('Oooger Booger');

?>


Heh, beaten by a few mins :p

Sweet, I see know! Thanks guys!