The Qt developers started to reduce their efforts on Phonon integration already during the later versions of Qt4, focussing on the Qt Multimedia and Qt Mobility modules instead. Though they did still support Phonon.
As you say, as of Qt5, Phonon is no longer supported. So look into Qt Multimedia instead, especially QAudioOutput.
As listed within their documentation under "Detailed Description", playing an audio file looks something like this:
QFile inputFile; // class member.
QAudioOutput* audio; // class member.
inputFile.setFileName("/tmp/test.raw");
inputFile.open(QIODevice::ReadOnly);
QAudioFormat format;
// Set up the format, eg.
format.setFrequency(8000);
format.setChannels(1);
format.setSampleSize(8);
format.setCodec("audio/pcm");
format.setByteOrder(QAudioFormat::LittleEndian);
format.setSampleType(QAudioFormat::UnSignedInt);
QAudioDeviceInfo info(QAudioDeviceInfo::defaultOutputDevice());
if (!info.isFormatSupported(format)) {
qWarning()<<"raw audio format not supported by backend, cannot play audio.";
return;
}
audio = new QAudioOutput(format, this);
connect(audio,SIGNAL(stateChanged(QAudio::State)),SLOT(finishedPlaying(QAudio::State)));
audio->start(&inputFile);