You are using the XML API of the www.casapilot.com website.
The API is via HTTPS, one example URI is:
https://www.casapilot.com/api/1/accommodations/calendar.xml?auth_token=hyXHjP8QdrRuX8q3FsbC&id=1049165
For HTTPs to work, PHP needs the openssl extension. The information is given on the related Stream Wrapper Page:
Note: HTTPS is only supported when the openssl extension is enabled.
The openssl extension is then used for all HTTPS "files" transparently with the stream-wrapper for all URIs starting with https://.
See as well the duplicate question:
- How to enable HTTPS stream wrappers
