Sorry for the delay in a response, life got busy.
I just attempted another run on making the SDL2_Mixer extension, I tried installing the opusfile-dev but found that there is no files avaiable under that name in "Apps downloader" , so i tried installing libopus-dev and libopus instead (assuming that they might suffice as an alternative), then I applied the complier flags (which I finally managed to get right) and a WARNING came up 'unable to find opusfile library...' I came this far so I attempted the code "find . -name Makefile -type f -exec sed -i 's/-g -O2//g' {} \;" but nothing seemed to happen, perhaps my processor is slow and I had to wait longer? I then tried to 'make'. Which raised an error of 'no Make file', or something along that line. I presume the Opusfile is required.
Is there a way to get this working without getting Opusfile from source?