It's likely that your Philips TV doesn't work with AirPlay natively. Perhaps it's built on Chromecast or Roku technology? I know many Philips TVs support them.
My model doesn't, but I use a Chromecast dongle - a separate device. Therefore, I mirror through apps compatible with Chromecast. Currently, I'm using this one https://apps.apple.com/us/app/docast-cast-and-mirror-to-tv/id6446948344
It works quite well with Chromecast, allowing you to mirror your screen and stream photos and videos, which is very convenient. The app also supports Roku and Fire TV. You can try it on your Philips TV. Simply download the app on your iPhone and follow the on-screen instructions