下面是我的程序代码，打印$getwxacodeunlimit的值一直为null

<?php
  $data=['scene'=>'test=1','width'=>430];
  $data=json_encode($data);
  $getwxacodeunlimit=$this->https_request($this->getwxacodeunlimit,$data);
  var_dump($getwxacodeunlimit);die;

function https_request($url,$data=null){
    $ch = curl_init();
   curl_setopt($ch, CURLOPT_URL, $url);
   curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
   curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 10);
   if($data){
      curl_setopt($ch, CURLOPT_POST, 1);
      curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
   }
   $result = curl_exec($ch);
   $info = json_decode($result);
   curl_close($ch); //释放资源 
   return $info;
}