The 23-year-old has signed a three-and-a-half-year contract with the Magpies.
“We’re delighted to complete a permanent deal for Danny,” said Newcastle chief Chris Hughton.
“He’s a player who has been with us since the summer and has played a key role during the first half of the season.
“Danny is a very popular lad in the dressing room and he took no time at all to settle in.
“He was always a player we wanted to keep at the club and he was very keen to stay given how much he’s enjoyed his time here.”
