Determines whether a node hook exists.
string $type: A string containing the node type.
$hook: A string containing the name of the hook.
string|false A string containing the function name or FALSE if it isn't found.
function node_hook($type, $hook) {
$base = node_type_get_base($type);
return module_hook($base, $hook) ? $base . '_' . $hook : FALSE;
}