Updating session variables without page refresh - php

Question

I'm using modal to display form. I want to validate form and show possible errors after clicking submit button. I don't want to close my modal after validation so I decided to use Ajax. Here is my code:
Modal:
<div class="modal fade" id="form-modal" tabindex="-1" role="dialog" aria-labelledby="myModalLabel">
<div class="modal-dialog" role="document">
<div class="modal-content">
<div class="modal-header">
<button type="button" class="close" data-dismiss="modal" aria-label="Close"><span aria-hidden="true">×</span></button>
<h4 class="modal-title" id="myModalLabel">Modal title</h4>
</div>
<div class="modal-body">
<form name="offer-form" id="offer-form" action="offers.php" method="post">
<label for="name-input">Name</label><br>
<?php
if (isset($_SESSION["name-error"])) {
echo "<p>".$_SESSION["name-error"]."</p>";
unset($_SESSION['name-error']);
}
?>
<input type="text" id="name-input" name="name"><br>
<input type="submit" id="submit-input" name="submit" value="Submit">
</form>
</div>
<div class="modal-footer">
<button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
<button type="button" class="btn btn-primary">Save changes</button>
</div>
</div>
</div>
Script:
<script type="text/javascript">
$(document).ready(function(){
$("#offer-form").submit(function(e){
e.preventDefault();
$.ajax({
type : 'POST',
data: $("#offer-form").serialize(),
url : 'validate.php',
success : function(data){
}
});
return false;
});
})
PHP:
<?php
session_start();
$_SESSION["name-error"] = "Error";
?>
The problem is that I have to refresh website to see error being displayed. How can I fix this?

Answer 1

Display the error with JQUERY... If you want PHP to process your $_SESSION you will need to reload the page (because PHP in on the server side).
Do an echo in your PHP file and catch the data in your success function
<?php
session_start();
$_SESSION["name-error"] = "Error";
echo "ERROR";
success : function(data){
if(data = "Error")
{
}
}

Answer 2

Your validation.php file
session_start();
$_SESSION["name-error"] = "Error";
$error = array('error' => $_SESSION["name-error"]);
echo json_encode($error);
Your Html
<label for="name-input">Name</label><br>
<p class='sessionError'></p>
Your ajax success funcion
success : function(data){
$('.sessionError').text(data.error);
}

Answer 3

return the value of the session to your ajax and using jquery append the error to the page:
Add the following to your success function
success : function(data){
$('label[for="name-input"]').html('</br>'+data.message)
}
in your php
<?php
session_start();
header('Content-Type: application/json');
$_SESSION["name-error"] = "Error";
echo json_encode(["message"=>$_SESSION["name-error"]]);
?