Ajax call on submit refreshing page - php

Question

Problem
My page seems to be defaulting to my PHP code instead of being handled asynchronously via ajax. As of now, my page just reloads as a blank screen, the input array successfully got passed over to the PHP, which is comforting, but I seem to just be doing something wrong with the ajax.
What I've tried
After viewing this link and this link, I still cant seem to get this figured out.
Current Standing
Here is the HTML:
<form class="cmxform" id="commentForm" method="" action="">
<fieldset>
<legend>Please provide your name, email address (won't be published) and a comment</legend>
<p>
<label for="spinner">How much do you love science? (optional)</label>
<input id="spinner" name="spinner">
</p>
<p>
<label for="cname">Name (required, at least 2 characters)</label>
<input id="cname" name="name" minlength="2" type="text" required>
</p>
<p>
<label for="cemail">E-Mail (required)</label>
<input id="cemail" type="email" name="email" required>
</p>
<p>
<label for="curl">URL (optional)</label>
<input id="curl" type="url" name="url">
</p>
<p>
<label for="aoi">Area of Interest (optional)</label>
<input id="aoi" type="text" name="aoi">
</p>
<p>
<label for="currprobs">Current Problems (optional)</label>
<input id="currprobs" type="text" name="currprobs">
</p>
<p>
<label for="ccomment">Your comment (required)</label>
<textarea id="ccomment" name="comment" required></textarea>
</p>
<p>
<input id="launch" type="submit" value="Submit">
</p>
</fieldset>
</form>
<div id="results"></div>
Here is the javascript:
$(document).ready(function(){
$("#commentForm").submit(function(event){
/*
var formData = {
'name' : $('input[name=name]').val(),
'email' : $('input[name=email]').val(),
};
*/
alert("SUCCESS?");
});
});
PHP code to return a div after the user has been validated:
<?php
$username = isset($_POST['name'])? trim($_POST['name']):'';
$email= isset($_POST['email'])? trim($_POST['email']):'';
echo '<div id=dynamicDiv>
<p>Hello, '.$username.'!</p>
<p>We look forward to contacting you at, '.$email.'</p>
</div>';
?>
Feedback
Any thoughts are appreciated, even intellectual conversation. Code snippets are idea, but I appreciate anything the community is able
Edit 1
I motified the javascript and php to reflect knowledgable input and best practice for PHP and AJAX calls, however the issue still remains.
Edit 2
My goal now is to just get an alert() statement working inside of my javascript, ajax will be the next step.

Answer 1

I think problem is here
$("#results").html = html_i;
You try change to
$("#results").html(html_i);
And in php you should check name and email
$username = isset($_POST['name'])? trim($_POST['name']):'';
$email= isset($_POST['email'])? trim($_POST['email']):'';

Answer 2

You should change input type="submit" to input type="button" and call Ajax on onclick function, Its resolve your problem because submit button submit form and Ajax call pending not reached to 400 state.