I've explained what's going on in the comments:
// This gives array(1) { [0]=> string(3) "PDO" }
$arrName = explode('_', $name);
// This gives string(3) "pdo"
$typename = strtolower(array_shift($arrName));
// This gives string(0) ""
$moduleName = strtolower(array_shift($arrName));
// This returns FALSE
if (count($arrName) > 0 )
{
$className = strtolower(array_shift($arrName));
}
else
{
// This gives string(0) ""
$className = $moduleName;
}
// This gives string(9) "pdo//.php"
$location = '' . $typename . '/' . $moduleName . '/' . $className . '.php';
However, as I assume you're using (or at least trying to use) the PHP Data Objects
extension, you need to make sure that it is installed.