If you are getting this notice “Undefined offset: 0 in /symfony/util/Spyc.class.php” in Symfony (especially after you clear your cache) check your yml files. You are most likely missing a colon somewhere or have some other error.
For example:
setting
id1: value1
id2: value2
should be (missing colon):
setting:
id1: value1
id2: value2
