Phil and Sharon were once a great love story but not anymore, there's no chemistry between them anymore and doesn't seem to be any real love of affection. I would no longer be surprised if Phil did dump Sharon in favour of reuniting with Shirley, Sharon is no longer the woman Phil fell in love with all those years ago. Sharon used to be strong, independent, intelligent woman however since returning in 2012 the writers have seen to it that Sharon is portrayed as a sad, desperate, needy, gold-digger. The old Sharon would never have latched onto a man in order to fund her latest business venture. Not only that but she's also became very bitchy, unpleasant and socially inept. If i was a new viewer who hadn't seen Sharon prior to 2012 i would have a very low opinion of her character.
I say let Phil and Shirley get back together the chemistry is there and they're very well suited, get Sharon away from Phil and start to rebuild her character back to the one we came to know and love last seen departing in a taxi in January 2006.