Explanation from Alexei Zakhlestin:



I noticed, that you limit yaml-documents only to the ones which 
provide arrays, which is not always true. yaml-document can consist of 
the single literal (string, null, number, etc) and still be valid. 
Currently, whenever syck_load() returns anything but array, you force 
result to be empty array().



Simple test-case:



<?php



require 'Horde/Yaml.php';



$doc = 'test';



var_dump(syck_load($doc));

var_dump(Horde_Yaml::load($doc));