How to send data without reloading page with cURL? - php

Question

I am trying log in a website which has security code for 2 days like you see below.
(By the way, I can get security number from html codes of web page.)
First, I have to connect to website and get the code(254), than post username, password and security number. But there is a big problem. I am getting security number and the page is reloading and the code is changing everytime when I try post to webpage this variables.
Here is my PHP code:
<?php
include('simple_html_dom.php');
$url = "http://example.com/index.php";
$useragent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36";
$tmpfname = dirname(__FILE__).'/cookies.txt';
$ch = curl_init(); // GET REQUEST
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_COOKIEJAR, $tmpfname);
curl_setopt($ch, CURLOPT_REFERER, $url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
curl_setopt($ch, CURLOPT_USERAGENT, $useragent);
$str = curl_exec($ch);
echo $str;
curl_close($ch);
preg_match('~<td><img src="number/(.*?).jpg"></td>~', $str, $securityNo); // I am gettin security number
echo $securityNo[1]; // It print true
$username = "USER";
$password = "PASS";
$postfields = array();
$postfields['UserName'] =$username; // Username
$postfields['Password'] = $password; // Password
$postfields['code'] = $securityNo[1]; // Code
$postfields['LOGIN'] = "LOGIN"; // BUTTON
$curl =curl_init();
curl_setopt($curl, CURLOPT_URL, $url);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
curl_setopt($curl, CURLOPT_FOLLOWLOCATION, 1);
curl_setopt($curl, CURLOPT_REFERER, $url);
curl_setopt($curl, CURLOPT_USERAGENT, $useragent);
curl_setopt($curl, CURLOPT_POST, 1);
curl_setopt($curl, CURLOPT_COOKIEFILE, $tmpfname);
curl_setopt($curl, CURLOPT_POSTFIELDS, $postfields);
curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, 0);
curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, 0);
$ret = curl_exec($curl);
curl_close($curl);
echo $ret;
?>
I printed screen both 'echo $str' (get request) and 'echo $ret' (post request) but there is different 2 codes in screen, not same code printed.
I researched on internet too much, but I got nothing. I can't solve this.
Thanks in advance!