Sizin ilacınız ajax.
Örnek vereyim ki farkım olsun
form.html
<html>
    <head>        
        <script type="text/javascript" src="prototype.js"></script>
        <script>
 
            function sendRequest() {
                new Ajax.Request("test.php", 
                    { 
                    method: 'post', 
                    postBody: 'name='+ $F('name'),
                    onComplete: showResponse 
                    });
                }
 
            function showResponse(req){
                $('show').innerHTML= req.responseText;
            }
        </script>
    </head>
 
    <body>
        <form id="test" onsubmit="return false;">
            <input type="text" name="name" id="name" >
            <input type="submit" value="submit" onClick="sendRequest()">
        </form>
 
        <div id="show"></div>
    </body>
 
</html>
test.php
<?php
 
if($_POST["name"] == "")
    echo "name is empty";
else
    echo "you typed ".$_POST["name"];
?>
gerekli kısımları kendinize göre düzenleyiniz.