JavaScript不在php输出ajax中运行

this is my index.php (submit a form by ajax and retrun an alert)

 <form>
     <input id="email" type="text">
     <input id="cellphone" type="text">
    <input type="button" value="submit" onclick='runajax()'/>
 </form>

<div id="display">

this is js code:

<script type="text/javascript">
        function runajax() {
            var xmlhttp;
            var val1=document.getElementById('email').value;

            var val2=document.getElementById('cellphone').value;

            if (window.XMLHttpRequest) {
                // code for IE7+, Firefox, Chrome, Opera, Safari
                xmlhttp = new XMLHttpRequest();
            } else {
                // code for IE6, IE5
                xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
            }

            xmlhttp.onreadystatechange = function() {
                if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
                    document.getElementById("display").innerHTML = xmlhttp.responseText;
                    console.log(xmlhttp.responseText);
                } 
            }
            xmlhttp.open("GET", "doForm.php?email="+val1+"&cellphone="+val2, true);
            xmlhttp.send(null);
        }
</script>

and this is "doForm.php"

<?php 
echo "your email is".$_GET['email'];
echo "<script>alert(your email is".$_GET['email'].")</script>";
?>

the problem is this

first echo in doform.php print currectly but second echo (include an alert javascript code) do not run!

how can I run javascript alert in php output?

try changing this line:

echo "<script>alert(your email is".$_GET['email'].")</script>";

to:

echo "<script>alert('your email is".$_GET['email']."')</script>";