The error received is:

checking for ffmpeg support…checking for ffmpeg headers… configure: error: ffmpeg headers not
found. Make sure you’ve built ffmpeg as shared libs using the –enable- shared option

This is due to missing header files in  “/usr/local/include/ffmpeg” directory.

Check whether the directory “/usr/local/include/ffmpeg” exists else create it.

mkdir /usr/local/include/ffmpeg

Then copy the header files.

cp -p /usr/local/src/ffmpeg/libavformat/avio.h /usr/local/include/ffmpeg
cp -p /usr/local/src/ffmpeg/libavformat/avformat.h /usr/local/include/ffmpeg
cp -p /usr/local/src/ffmpeg/libavcodec/avcodec.h /usr/local/include/ffmpeg

You need to reinstall ffmpeg. After installing ffmpeg, install ffmpeg-php.