Many donations came from people in the community where Mr Connolly had worked as a cop.
"Thank you for your amazing work on the front line. Wishing you all the best as you head into this fight," wrote one woman who donated.
"Thank you so very much for your service to the community. The police do an outstanding job, often without thanks....best wishes to you and your family," said another.
Mr Connolly was off-duty and walking his dog when he tried to stop two girls fighting near his home in Tuakau.
As he went to help, he was king-hit from behind before up to 30 teenagers joined the attack, leaving him with a fractured skull, a collapsed lung, a broken jaw and a broken ankle.
Ten youths were later charged with his assault, and the then Police Minister, Judith Collins, said he was a hero.
His family and colleagues feared he would die, but Mr Connolly eventually returned to work after having a metal plate inserted in his forehead.
Last month, the 44-year-old was told he had throat cancer.
• To support John Connolly go to Givealittle fundraising page.