The 34-year-old Scottish footballer issued an appeal to fans to help find the man who kept his father-in-law alive after he suffered a heart attack on Sunday.
Gallagher's father-in-law, Jimmy Smith, collapsed at 10.30am at a petrol station in Preston Road, Lytham.
Mr Smith's life was saved by a man who rushed to his aid and performed CPR until paramedics arrived at the scene.
The PNE star said the unknown 'hero' had saved his father-in-law's life.
Gallagher said: "His heart totally stopped for 20 minutes.
"Luckily, a bystander performed excellent CPR until the ambulance arrived and no doubt saved his life.
"We have no contact details for the this man, but would like to thank him.
"My father-in-law is still in a critical condition and being monitored in intensive care.
"But he is currently breathing and we're taking it hour by hour."
The midfielder said he had decided to play in Sunday's FA Cup defeat at home to Doncaster Rovers because 'that's what Jimmy would have wanted'.
"I still played today because that's what Jimmy would always want with his 'get on with it/run it off' attitude", Gallagher said.
But a shaken Gallagher said his father-in-law had faced certain death if not for the bravery and quick thinking of the man at Lytham Service Station.
He said: "Thank goodness it happened at the petrol station and not at home alone.
"And thank god for that man."