raw code for handling Google Analytics clientId in a separate secure https cookie and writing it to the dataLayer to be used by ga tracking tags

secure_ga_cookie.php

<?php
  //optional: set this to desired cookie domain. example ".mydomain.de" to cover all subdomains  
  $domain = "";
  //get client id from secure http cookie
  $cid = ($_COOKIE['_hga']); 
  //new user? get _ga cookie client id, if exists
  if (!isset($cid)) $cid = ($_COOKIE['_ga']); 
  //still no id? create new cliend id
  if (!isset($cid)) $cid = rand(10000, 99999).rand(20000, 99999).".".time(); 
  //Set secure http cookie with 2 years lifetime
  setcookie("_hga", $cid, time()+60*60*24*365*2, 
            "/; samesite=strict'", $domain, 
            $secure = true, $httponly = true);
  //write script to push client id to dataLayer 
  echo "<script>\n".
  "window.dataLayer = window.dataLayer || [];\n".
  "window.dataLayer.push({\n".
  "'event': 'clientIdReady',\n".
  "'secureClientId': '".$cid."'\n".
  "});\n".
  "</script>";
  //optional: set global js variable for direct implementations of ga code
  //echo "<script>window._secureClientId='".$cid."';</script>";
?>

Hello @awaismun, just enter your domain starting with a dot to cover all hosts. See comment in the very first line 😉