写一个可以直接调用的jssdk.php

以下是一个简单的 jssdk.php 文件的示例，它包含了获取签名所需的函数：

<?php

$appId = "your app id";
$appSecret = "your app secret";

// 获取签名
function getSignature() {
  global $appId, $appSecret;

  // 获取随机字符串
  $nonceStr = getNonceStr();

  // 获取时间戳
  $timestamp = time();

  // 获取当前 URL
  $url = "http://$_SERVER[HTTP_HOST]$_SERVER[REQUEST_URI]";

  // 将参数按照字典序排序
  $parameters = array(
    "noncestr" => $nonceStr,
    "timestamp" => $timestamp,
    "url" => $url,
  );
  ksort($parameters);

  // 将参数拼接成字符串
  $string1 = "";
  foreach ($parameters as $key => $value) {
    $string1 .= "$key=$value&";
  }
  $string1 = rtrim($string1, "&");

  // 将签名所需的三个参数拼接成字符串
  $string2 = "jsapi_ticket=$jsapiTicket&noncestr=$nonceStr&timestamp=$timestamp&url=$url";

  // 使用 SHA-1 算法生成签名
  $signature = sha1($string1);

  return $signature;
}

// 获取随机字符串
function getNonceStr() {
  $characters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
  $nonceStr = "";
  for ($i = 0; $i < 16; $i++) {
    $nonceStr .= $characters[mt_rand(0, strlen($characters) - 1)];
  }
  return $nonceStr;
}

// 获取 jsapi_ticket
function getJsApiTicket() {
  global $appId, $appSecret;

  // 从缓存中获取 jsapi_ticket
  $jsapiTicket = "your cached jsapi ticket";
  if ($jsapiTicket) {
    return $jsapiTicket;
  }

  // 从微信服务器获取新的 jsapi_ticket
  $accessToken = getAccessToken();