No response from server in my Ionic registration system - php

Question

I am making a simple registration system in Ionic Cordova. I am sending the data from the form to server through an AJAX call but I am not getting anything in response form the sever. When I made a different conventional form and dent the data to the same script I got the proper response. I am able to figure out the issue.
form:-
<div class="list" id="register">
<label class="item item-input item-floating-label">
<span class="input-label">Name</span>
<input type="text" placeholder="Name" id="name">
</label>
<br>
<label class="item item-input item-floating-label">
<span class="input-label">Email</span>
<input type="email" placeholder="Email" id="email">
</label>
<br>
<label class="item item-input item-floating-label">
<span class="input-label">Password</span>
<input type="password" placeholder="Password" id="pass">
</label><br>
<button class="button button-full button-assertive" id="signup">
Submit
</button>
AJAX call:-
$(document).ready(function(){
$("#signup").click(function(){
console.log("Button clicked");
var name=$("#name").val();
var email=$("#email").val();
var pass=$("#pass").val();
var dataString="name="+name+"&email="+email+"&pass="+pass+"&signup=";
if($.trim(name).length>0 && $.trim(email).length>0 && $.trim(pass).length>0)
{
$.ajax({
type: "POST",
url: "http://127.0.0.1/ionic/reg.php",
data: {dataString: dataString,signup:true},
success: function(data){
if(data =="success")
{
alert("Thank you for Registering with us! you can login now");
}
else if(data =="exist")
{
alert("Hey! You alreay has account! you can login with us");
}
else if(data =="failed")
{
alert("Something Went wrong");
}
}
});
}
return false;
});
});
PHP script:-
<?php
header('Access-Control-Allow-Origin: *');
include 'db_connect.php';
if(isset($_POST['signup']))
{
$name=trim($_POST['name']);
$email=trim($_POST['email']);
$password=trim($_POST['pass']);
$login=mysqli_num_rows(mysqli_query($con,"select * from `phonegap_login` where `email`='$email'"));
if($login!=0)
{
echo "exist";
}
else
{
$q=mysqli_query($con,"insert into `phonegap_login` (`name`,`email`,`password`) values ('$name','$email','$password')");
if($q)
{
echo "success";
}
else
{
echo "failed";
}
}
echo mysql_error();
}
?>