This example will echo a 8 digit random number to screen

<?php

echo substr(mt_rand(),0,8);

?>

Thanks very much.

Here's a short example to generate alphanumeric codes. Changing the string passed to str_split alone will let you use an arbitrary set of characters.

<?php

$charset=str_split("0123456789abcdefghijklmnopqrstuvwxyz");

$output="";

for($i=0;$i<8;$i++){

$output.=$charset[rand(0,count($charset)-1)];

}

echo $output;

?>