The 19-year-old Leeds lad was offered fresh terms recently and his signature follows on from contract extensions agreed by Lewis Cook, Tyler Denton, Jake Skelton, Luke Parkin and Alex Purver.
Kalvin, an Academy graduate, joined the club at age of 14 and progressed through the ranks at Thorp Arch before signing his first professional deal last summer.
The former Wortley junior was a regular for the Under-21s during 2014/15 and scored six times in his 23 appearances and earned many plaudits along the way with Jason Blunt’s development squad.
Phillips sampled experience in the senior match-day squad and featured as an unused substitute several times before being handed his full debut in the televised trip on Easter Monday to Wolverhampton Wanderers, when United lost 4-3.
Phillips was handed his home bow the following Saturday (April 11) against Cardiff City and memorably found the net on his Whites debut – while also claiming the man of the match award.