is apple provide web api to get calendar events

i develop an PHP Web App, where users can create and edit events inside.

Now i would like to sync these events with the iCloud Calendars from each user.

The PHP Web App should read,create and edit the events from the icloud calenders.

Is that possible?

I could realy find a API or Docomentation.

It would be important that i can make that happend without the use of Xcode.