2 way SYNC Calendar API - google, outlook and ical

Looking for an experienced person to do Rest Api - Calendar Sync - Google, Outlook and Apple using PHP. You have have done this before. We have hired a team but we can't use their code in our iOS app. The code has to work with 2 way sync with our calendar app and we have to make this work right away. We want add, del, edit from both sides to reflect data. Code will include: 1. authentication to all 3 services and add add sync option in our database 2. Sync via cron to make sure 2 way sync works