Laravel 5.4调用未定义的函数App \ iconv（）

I have uploaded my project to a server, and now it is giving me problems, which can be ?, in local the project runs perfectly. this is the code of my function

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Gateway extends Model
{
     function _doPost($query) {
        $ch = curl_init();
        curl_setopt($ch, CURLOPT_URL, "https://secure.nmi.com/api/transact.php");
        curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 30);
        curl_setopt($ch, CURLOPT_TIMEOUT, 30);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
        curl_setopt($ch, CURLOPT_HEADER, 0);
        curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);

        curl_setopt($ch, CURLOPT_POSTFIELDS, $query);
        curl_setopt($ch, CURLOPT_POST, 1);

        if (!($data = curl_exec($ch))) {
            return ERROR;
        }
        $wm_string = iconv("windows-1251", "UTF-8", $data);
        parse_str(urldecode($wm_string), $result);
        $data=json_encode($result, JSON_UNESCAPED_UNICODE);
        curl_close($ch);
        unset($ch);

        $this->datos=$data;
        return $this->datos;
      } 
       }

the error is

Call to undefined function App\iconv() in this line

    $wm_string = iconv("windows-1251", "UTF-8", $data);

can be this a server problem? or maybe I must to download some package to my project?

You may need to ask your hosting provider to give/install PHP compiled with iconv. Because by default php comes with iconv unless explicitly compiled without it.

This extension is enabled by default, although it may be disabled by compiling with --without-iconv .

iconv: http://php.net/manual/en/book.iconv.php

iconv installation: http://php.net/manual/en/iconv.installation.php