$.ajax({
  type: "POST",
  url: "save.php",
  data: {
     imgBase64: data
  }
}).done(function(o) {
  //done
});

var request = new XMLHttpRequest();
request.open('POST', 'save.php', true);
request.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded; charset=UTF-8');
request.send(data);