Hocam Api vs. Bilginiz varsa aşağıda yer alan linkten kodlamayı yaparsınız:
https://github.com/agliottone/youtube-dl-mp3-php/
https://davidwalsh.name/youtube-ffmpeg-mp3-conversion
https://github.com/MichaelBelgium/Youtube-to-mp3-API
https://github.com/coolguruji/youtube-to-mp3-converter-php-script