[RESOLVED] How to loop

[PartialReptile]

Hey,

can anyone help with how to put somethign like the following into a loop, I can't get my head round it, infact, I can't even figgure out which loop type to use:o

//gen randomID
$chars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
$length = 40;
$max_i = strlen($chars)-1;
$randomID = '';
for ($i=0;$i<$length;$i++)
{
	$randomID .= $chars{mt_rand(0,$max_i)};
}

//see if Random ID is in db
$sql ="SELECT randomID FROM table WHERE randomID='$randomID' LIMIT 1";
$rs = mysql_query( $sql, $con )
	or die ('error - sql1');

$num = mysql_num_rows( $rs );
if( $num != 0 )
{	
	//if it is, generate a new one (and repeat to make that isn't there?)
	$chars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
	$length = 40;
	$max_i = strlen($chars)-1;
	$randomID = '';
	for ($i=0;$i<$length;$i++)
	{
		$randomID .= $chars{mt_rand(0,$max_i)};
	}
}
else
{
//keep $randomID and move on
}

Ultimately all I'm trying to do is:

generate a random string
see if it's already present in a db,
if it is, regenerate
and repeat the process 'til one that isn't present in the DB is generated?

I'd like to understand what I'm doing, so that if I come accross a similar need with modifications leter, I won't need to ask the same questions again, so I'm not really looking for a code example, more a bit of direction on how I should be approacing it (what type of loop to use, should I be using some type of function, etc)

If anyone's able to help, thanks for your time.

[jib0]

This is what you can do:

function random_string($length) {
	$chars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
	$max_i = strlen($chars) - 1;
	$randomID = '';
	for ($i = 0; $i < $length; $i++)  

    $randomID .= $chars{mt_rand(0, $max_i)}; 

   return $randomID;
}

function random_id() {
	do {
		$randomID = random_string(40);
		$sql ="SELECT randomID FROM table WHERE randomID='$randomID' LIMIT 1";
		$rs = mysql_query($sql, $con)
			or die('error - sql1');
	} while (mysql_num_rows($rs) > 0);

return $randomID;
}

[PartialReptile]

Ouch, that turned out to be a lot simpler than I thought :o I really need to spend a lot more time on functions and loops.

many, many thank yous Mr. jib0. Resolved!

[bpat1434]

Alternatively you could use a timestamp and use [man]sha1/man to hash it for a "random" string. That's just another alternative.