<form method="post" id="myform">
        <input type="text"  placeholder="Your name" autofocus required pattern="[a-z]{1,15}"/> 
        <input type="text" placeholder="Phone-number" required pattern="[0-9]{6,15}"/>
        <input type="email" placeholder="Email" required/> 
        <input class="button" type="button" onclick="sendMyForm();"  rel="reg_form" value="request call"/>
</form>

<script type="text/javascript" language="javascript">
 	function sendMyForm() {
 	  var msg   = $('#myform').serialize();
        $.ajax({
          type: 'POST',
          url: 'res.php',
          data: msg,
          success: function(data) {

    $('.popup').fadeIn(500);
    $("body").append("<div id='overlay'></div>");
    $('#overlay').show().css({'filter' : 'alpha(opacity=80)'});

          },
          error:  function(xhr, str){
	    alert('Возникла ошибка: ' + xhr.responseCode);
          }
        });
 
    }
</script>