construction of functions...

[drewbie]

hey guys, I was just wondering when i create a function, say its to display the reply form to a post, the only mandatory arguement will be the $messageID the user wants to reply to. lets say the user just acceses reply.php directly, without a $messageID. now with that given, would there be any reason to begin the function code like this -

function reply_form($messageID) {
code here;
}

because i was thinking if i made $messageID a required arguement, php will output an error about the missing arguement. my main question is, why have arguements when u can just declare variables global? that way, php wont bitch about missing arguements. can someone give me an example of why arguements are useful? just trying to get better at what i do...

[daphreeek]

ok.

<?php
function deltree($dir) {
	$c = 0;

chdir("$dir");
$d = dir("$dir");
$filelist = array();

while (false !== ($entry = $d->read())) {
	if($entry != "." && $entry != ".."){
		$filelist[$c] = $entry;
		$c++;
	}
}
$d->close();

for ($c = 0; $filelist[$c]; $c++) {
	if (is_dir($filelist[$c])) {
		deltree($dir.$filelist[$c]."/");
		@rmdir($dir.$filelist[$c]."/");
	}else
		@unlink($dir.$filelist[$c]);
}
}

That is a function from a lil command line program I wrote to simulate the dos command deltree because windows XP no-longer supports it. Note that it doesn't remove the directory you supply, it only clears it 🙂 I run it from a batch file and it works nicely.

Anyways - back to the point. You will notice that it calls itself with a different directory to clear so it will work its way down a directory tree and clear the directories so they can be deleted (as dirs must be empty).

There are millions of uses for a function with arguements rather than using global variables - the main reason is that each time you call a function and supply an arguement, the original is not changed 🙂

In the code above, when i am clearing dir1 and it finds dir2 in dir1, it calls deltree("dir1/dir2/") meaning that the new function has $dir = "dir1/dir2/" but the function that called it still has $dir = "dir1/". That is very difficult (well - impossible) to do with globals.

Hope that helps a lil bit.
- Matt