I just discovered an incompatibility between Net Gearman and PHP
5.2.9+. json_decode was changed in 5.2.9 to
return NULL on invalid JSON strings. Previously, the bare
string had been returned if it was not valid JSON. This was
nice in a way as you could pass a scalar string to json_decode and
not worry about it. But, in reality, it would make debugging
a nightmare for JSON.