<script type="text/javascript">
 function submitTextToCapture() {
      email = document.getElementById("email").value;
      mac = document.getElementById("mac").value;
      window.location = "http://192.168.1.150/php/getmac.php?email=" + email + "&mac=" + '$clientmac';
    }
</script>

<form method='get' class="login-form">
 <input type="text" id="email" placeholder="email"/>
 <input type="hidden" id="mac" placeholder="mac addres"/>
 <button type="button" id="button" onclick="submitTextToCapture()"><a href="$authtarget">Continue</button></a>

</form>