如何使用PHP实现微信小程序的头像制作功能？

// 选择上传头像
chooseAvatar: function() {
  wx.chooseImage({
    count: 1,
    success: function(res) {
      var avatarUrl = res.tempFilePaths[0];
      // 将选择的头像发送给服务器端进行处理
      wx.uploadFile({
        url: 'https://example.com/upload_avatar.php',
        filePath: avatarUrl,
        name: 'avatar',
        success: function(res) {
          console.log('上传头像成功');
        },
        fail: function(res) {
          console.log('上传头像失败');
        }
      });
    }
  });
},

// 选择头像框
chooseFrame: function() {
  wx.chooseImage({
    count: 1,
    success: function(res) {
      var frameUrl = res.tempFilePaths[0];
      // 将选择的头像框发送给服务器端进行处理
      wx.uploadFile({
        url: 'https://example.com/upload_frame.php',
        filePath: frameUrl,
        name: 'frame',
        success: function(res) {
          console.log('上传头像框成功');
        },
        fail: function(res) {
          console.log('上传头像框失败');
        }
      });
    }
  });
},

// 制作头像
createAvatar: function() {
  wx.request({
    url: 'https://example.com/create_avatar.php',
    method: 'POST',
    success: function(res) {
      console.log('头像制作成功');
      var avatarUrl = res.data.avatarUrl;
      // 显示生成的头像
      wx.previewImage({
        urls: [avatarUrl]
      });
    }
  });
}

<?php
// 上传头像
$avatarTempPath = $_FILES['avatar']['tmp_name'];
$avatarSavePath = 'avatar/' . $_FILES['avatar']['name'];
move_uploaded_file($avatarTempPath, $avatarSavePath);

// 上传头像框
$frameTempPath = $_FILES['frame']['tmp_name'];
$frameSavePath = 'frame/' . $_FILES['frame']['name'];
move_uploaded_file($frameTempPath, $frameSavePath);

// 合成头像
$avatar = imagecreatefromjpeg($avatarSavePath);
$frame = imagecreatefrompng($frameSavePath);
imagecopy($avatar, $frame, 0, 0, 0, 0, imagesx($frame), imagesy($frame));
$outputPath = 'output/avatar_' . time() . '.jpg';
imagejpeg($avatar, $outputPath);
imagedestroy($avatar);
imagedestroy($frame);

// 返回生成头像的URL
echo json_encode(['avatarUrl' => $outputPath]);

?>