At the end of the in_array statement below what is this- ? $orderdir: "ASC"
Is this the default behavior if $orderdir evaluates to false

Code:
(in_array($orderdir, array("ASC", "DESC")) ? $orderdir : "ASC");

That is the ternary operator, it is somewhat equivalent to an if-then-else statement.

Basically that code is saying that if $orderdir is contained within the array("ASC", "DESC") then return $orderdir; otherwise default to return the value "ASC". The result is a string. To give you an idea as to it's logic, it's roughly equivalent to:

PHP Code:

{
   if(in_array($orderdir, array("ASC", "DESC")) 
      return $orderdir;
   else
      return "ASC";
} 


References:
http://us3.php.net/manual/en/languag...arison.ternary
http://us2.php.net/in_array