$api = 'https://api.weixin.qq.com/sns/jscode2session?appid={$appId}&secret={$secret}&js_code={$code}&grant_type=authorization_code';

function httpGet($url) {
    $curl = curl_init();
    curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($curl, CURLOPT_TIMEOUT, 500);
    curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, true);
    curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, true);
    curl_setopt($curl, CURLOPT_URL, $url);

    $res = curl_exec($curl);
    curl_close($curl);

    return $res;
}

$str = httpGet($api);

echo  $str;

返回到前台 提示 40013 非法appid 这是为什么呢?