2012 blew the lid off of 1931's prior gold standard for warmth in Philadelphia, breaking the record by nearly seven tenths of a degree. However, it wasn't a year where the warmest high nor warmest low temperature on record was recorded over the course of the year.
Those honors belong to 1991 (high) and 1931 (low), respectively.
Last year's average high of 67.33 degrees missed the record for daily high warmth by nine hundredths of a degree, a pretty tiny amount in the grand scheme of things but enough to rank second on the warm charts. The low average of 50.45 degrees missed the record by just over two tenths of a degree, again good enough for second place.
To be fair, the 2012 average daily low temperature did set a record for the warmest low temperature at the Airport, where daily low temperatures have been tracked since 1940. Prior to 1940, the official recording site bounced around various locations in Center City. However, average temperatures aren't based solely on either the high or low...but it is neat to note that this year's record was achieved without breaking either the record for warmest highs in a year or the warmest lows.