如何创建签名框并使用php将签名提交(发布)到另一个页面？

<canvas id="signatureCanvas" width="500" height="200"></canvas>

var canvas = document.getElementById('signatureCanvas');
var ctx = canvas.getContext('2d');
var isDrawing = false;
var lastX = 0;
var lastY = 0;

canvas.addEventListener('mousedown', function(e) {
  isDrawing = true;
  [lastX, lastY] = [e.offsetX, e.offsetY];
});

canvas.addEventListener('mousemove', function(e) {
  if (!isDrawing) return;
  ctx.beginPath();
  ctx.moveTo(lastX, lastY);
  ctx.lineTo(e.offsetX, e.offsetY);
  ctx.stroke();
  [lastX, lastY] = [e.offsetX, e.offsetY];
});

canvas.addEventListener('mouseup', function() {
  isDrawing = false;
});

var submitBtn = document.getElementById('submitBtn');
var signatureInput = document.getElementById('signatureInput');

submitBtn.addEventListener('click', function() {
  var signatureData = canvas.toDataURL(); // 转换为Base64编码
  signatureInput.value = signatureData;
});

$signatureData = $_POST['signatureInput'];
// 进行签名数据的处理