如何在Wordpress中设置会话和Cookie中的动态变量

I am trying to store dynamic variable from external link ?dynamic=a_12_bc and put into the link look like this http://www.myweb.com?tracker=a_12_bc First time it always show the dynamic link but when i refresh and click on other page it shows ?tracker=[object][Object].

<?php session_start(); 
 echo $_GET['dynamic'];
if( isset($_GET['dynamic']))
{
  $cookie_name = "dynamic";
  $cookie_value = $_GET['dynamic'];
  setcookie($cookie_name, $cookie_value, time() + (86400 * 30), "/");
  $_SESSION["dynamic"] = $cookie_value;
  }
else
{   
 $_SESSION["dynamic"] = $_COOKIE['dynamic'];
 }?>
 Button Link
<a href="https://www.myweb.com/?tracker=<?php echo($_SESSION['dynamic']);?>" target="_blank">LOG IN</button></a>

Can you please tell me how to maintain a session on other pages

Check whether the cookie has been set, before assigning it to the session by adding isset() in your code.

if(isset($_GET['dynamic']))
{
   $cookie_name = "dynamic";
   $cookie_value = $_GET['dynamic'];
   setcookie($cookie_name, $cookie_value, time() + (86400 * 30), "/");
   $_SESSION["dynamic"] = $cookie_value;
}
else if(isset($_COOKIE['dynamic'])) {
   $_SESSION["dynamic"] = $_COOKIE['dynamic'];
}
else
{
   //something here
}

if the cookie is not set, try adding the domain in setcookie() method,

setcookie( $cookie_name , $cookie_value , time() + (86400 * 30), '/', COOKIE_DOMAIN );

If you need more information you can refer this link https://premium.wpmudev.org/blog/set-get-delete-cookies