The 19-year-old will spend a month at the League Two side and is likely to be given a run-out in Monday's pre-season friendly against Banbury United.
Philliskirk - who can play as a second striker or in midfield - started his career at Oldham before then Chelsea boss Jose Mourinho took him to Stamford Bridge for an undisclosed fee.
Wilder feels the former England Under-17 international will be a useful addition to the ranks and told the club's official website: "He's a young prospect I saw at Oldham as a kid and then Chelsea bought him for quite big money.
"It comes to a stage at 19 where he maybe needs to go and get involved with a senior club. He is a young boy but I think maybe people underestimate the level we are playing at now.
"We felt we needed an extra body in and he will benefit from the time here. Chelsea play three up front so he is used to playing in that. If he does well then he has a great opportunity here."