php实现支付宝当面付（扫码支付）功能

<?php
header('Content-type:text/html; Charset=utf-8');
$appid = 'xxxxx'; //https://open.alipay.com 账户中心->密钥管理->开放平台密钥，填写添加了电脑网站支付的应用的APPID
$notifyUrl = 'http://www.xxx.com/alipay/notify.php';   //付款成功后的异步回调地址
$outTradeNo = uniqid();   //你自己的商品订单号
$payAmount = 0.01;     //付款金额，单位:元
$orderName = '支付测试';  //订单标题
$signType = 'RSA2';    //签名算法类型，支持RSA2和RSA，推荐使用RSA2
//商户私钥，填写对应签名算法类型的私钥，如何生成密钥参考：https://docs.open.alipay.com/291/105971和https://docs.open.alipay.com/200/105310
$saPrivateKey='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';
$aliPay = new AlipayService($appid,$returnUrl,$notifyUrl,$saPrivateKey);
$result = $aliPay->doPay($payAmount,$outTradeNo,$orderName,$returnUrl,$notifyUrl);
$result = $result['alipay_trade_precreate_response'];
if($result['code'] && $result['code']=='10000'){
  //生成二维码
  $url = 'http://pan.baidu.com/share/qrcode?w=300&h=300&url='.$result['qr_code'];
  echo "<img src='{$url}' style='width:300px;'><br>";
  echo '二维码内容：'.$result['qr_code'];
}else{
  echo $result['msg'].' : '.$result['sub_msg'];
}
class AlipayService
{
  protected $appId;
  protected $returnUrl;
  protected $notifyUrl;
  //私钥文件路径
  protected $rsaPrivateKeyFilePath;
  //私钥值
  protected $rsaPrivateKey;
  public function __construct($appid, $returnUrl, $notifyUrl,$saPrivateKey)
  {
    $this->appId = $appid;
    $this->returnUrl = $returnUrl;
    $this->notifyUrl = $notifyUrl;
    $this->charset = 'utf8';
    $this->rsaPrivateKey=$saPrivateKey;
  }
  /**
   * 发起订单
   * @param float $totalFee 收款总费用 单位元
   * @param string $outTradeNo 唯一的订单号
   * @param string $orderName 订单名称
   * @param string $notifyUrl 支付结果通知url 不要有问号
   * @param string $timestamp 订单发起时间
   * @return array
   */
  public function doPay($totalFee, $outTradeNo, $orderName, $returnUrl,$notifyUrl)
  {
    //请求参数
    $requestConfigs = array(
      'out_trade_no'=>$outTradeNo,
      'total_amount'=>$totalFee, //单位 元
      'subject'=>$orderName, //订单标题
    );
    $commonConfigs = array(
      //公共参数
      'app_id' => $this->appId,
      'method' => 'alipay.trade.precreate',       //接口名称
      'format' => 'JSON',
      'charset'=>$this->charset,
      'sign_type'=>'RSA2',
      'timestamp'=>date('Y-m-d H:i:s'),
      'version'=>'1.0',
      'notify_url' => $notifyUrl,
      'biz_content'=>json_encode($requestConfigs),
    );
    $commonConfigs["sign"] = $this->generateSign($commonConfigs, $commonConfigs['sign_type']);
    $result = $this->curlPost('https://openapi.alipay.com/gateway.do',$commonConfigs);
    return json_decode($result,true);
  }
  public function generateSign($params, $signType = "RSA") {
    return $this->sign($this->getSignContent($params), $signType);
  }
  protected function sign($data, $signType = "RSA") {
    $priKey=$this->rsaPrivateKey;
    $res = "-----BEGIN RSA PRIVATE KEY-----\n" .
      wordwrap($priKey, 64, "\n", true) .
      "\n-----END RSA PRIVATE KEY-----";
    ($res) or die('您使用的私钥格式错误，请检查RSA私钥配置');
    if ("RSA2" == $signType) {
      openssl_sign($data, $sign, $res, version_compare(PHP_VERSION,'5.4.0', '<') ? SHA256 : OPENSSL_ALGO_SHA256); //OPENSSL_ALGO_SHA256是php5.4.8以上版本才支持
    } else {
      openssl_sign($data, $sign, $res);
    }
    $sign = base64_encode($sign);
    return $sign;
  }
  /**
   * 校验$value是否非空
   * if not set ,return true;
   *  if is null , return true;
   **/
  protected function checkEmpty($value) {
    if (!isset($value))
      return true;
    if ($value === null)
      return true;
    if (trim($value) === "")
      return true;
    return false;
  }
  public function getSignContent($params) {
    ksort($params);
    $stringToBeSigned = "";
    $i = 0;
    foreach ($params as $k => $v) {
      if (false === $this->checkEmpty($v) && "@" != substr($v, 0, 1)) {
        // 转换成目标字符集
        $v = $this->characet($v, $this->charset);
        if ($i == 0) {
          $stringToBeSigned .= "$k" . "=" . "$v";
        } else {
          $stringToBeSigned .= "&" . "$k" . "=" . "$v";
        }
        $i++;
      }
    }
    unset ($k, $v);
    return $stringToBeSigned;
  }
  /**
   * 转换字符集编码
   * @param $data
   * @param $targetCharset
   * @return string
   */
  function characet($data, $targetCharset) {
    if (!empty($data)) {
      $fileType = $this->charset;
      if (strcasecmp($fileType, $targetCharset) != 0) {
        $data = mb_convert_encoding($data, $targetCharset, $fileType);
        //$data = iconv($fileType, $targetCharset.'//IGNORE', $data);
      }
    }
    return $data;
  }
  public function curlPost($url = '', $postData = '', $options = array())
  {
    if (is_array($postData)) {
      $postData = http_build_query($postData);
    }
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_POST, 1);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $postData);
    curl_setopt($ch, CURLOPT_TIMEOUT, 30); //设置cURL允许执行的最长秒数
    if (!empty($options)) {
      curl_setopt_array($ch, $options);
    }
    //https请求 不验证证书和host
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
    curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false);
    $data = curl_exec($ch);
    curl_close($ch);
    return $data;
  }
}