How to write arraybuffer into database using php

Question

I use javascript with function createAnalyser() to create visualization for mp3 tracks, but the process of getting buffers too long.

Therefore, I intend to write buffers into the database, when play the song then the extraction buffers more quickly, that is my thought.

In my code, I use XMLHttpRequest() to receive the arraybuffer from mp3 files, but I don't know how to put arraybuffer into the database.

var request = new XMLHttpRequest();
request.open('GET', 'music.mp3', true);
request.responseType = 'arraybuffer';
request.onload = function() {
    context.decodeAudioData(request.response, function(buffer) {
        $.post('insert.php', {
            data: buffer
        }, function(res) {
            alert(res);
        });
    });
}
request.send();

And here is my PHP code:

<?php
$data = @$_POST['data'];
if (!$data) echo 'No data';
else {
    $open = fopen('audio.txt', 'a+');
    fwrite($open, $data);
    fclose($open);
    echo 'Done!';
}
?>

Please help me!