jQuery lightbox form not submitting data - php

Question

I've looked all over the place and it seems that people only want to open a lightbox AFTER submitting a form. I however want to submit the form FROM a lightbox. All my code works until I put the form into a lightbox so I'm wondering if this is even possible.
Form submit code (PHP):
if(isset($_POST['updatemain'])) {
$company = $_POST['conameu'];
$vault = $_POST['vnameu'];
$q = "UPDATE siteinformation SET SiteName = :company, VaultName = :vault";
$query = $db->prepare($q);
$results = $query->execute(array(
":company" => $company,
":vault" => $vault
));
header('Location: vault.php');
}
Form in the lightbox code:
<div class="backdrop"></div>
<div class="box"><div class="close"><img src="images/close.png" /></div>
<fieldset>
<legend>Pick a Section to Work on</legend>
<div id="prompt">Select a Section:</div>
<div id="answer">
<select id="sectionchange">
<option value="main">Main Titles</option>
<option value="organ">Emergency Organizations</option>
<option value="number">Common Numbers</option>
<option value="website">Common Websites</option>
<option value="quicklink">Quick Links</option>
</select>
</div>
</fieldset>
<div id="mainsection">
<form id="updatemain" action="" method="post">
<fieldset>
<legend><strong>Main Title Information</strong></legend>
<div id="prompt">Client Company Name:</div><div id="answer"><input type="text" name="conameu" id="conameu" /></div>
<div id="prompt">Web Tool Name:</div><div id="answer"><input type="text" name="vnameu" id="vnameu" /></div>
<div id="prompt"><input type="submit" id="updatemain" value="Update Information" /></div>
</fieldset>
</form>
</div>
</div>
</div>
Like I said, this works FINE until it is in the light box so I'm kind of stumped at this point.
Any ideas?
Thanks in advance for your time!

Answer 1

Per the comment section:
Add a name attribute with the value updatemain to your submit button.
Without this, PHP will not have a POST value $_POST['updatemain'] set, so the first if statement will always be false.

Answer 2

Updated to reflect that the "name" must be present in the submit button for this to work, even though for whatever reason it didnt need to be before. Thanks again #andbeyond
<div class="backdrop"></div>
<div class="box"><div class="close"><img src="images/close.png" /></div>
<fieldset>
<legend>Pick a Section to Work on</legend>
<div id="prompt">Select a Section:</div>
<div id="answer">
<select id="sectionchange">
<option value="main">Main Titles</option>
<option value="organ">Emergency Organizations</option>
<option value="number">Common Numbers</option>
<option value="website">Common Websites</option>
<option value="quicklink">Quick Links</option>
</select>
</div>
</fieldset>
<div id="mainsection">
<form id="updatemain" action="" method="post">
<fieldset>
<legend><strong>Main Title Information</strong></legend>
<div id="prompt">Client Company Name:</div><div id="answer"><input type="text" name="conameu" id="conameu" /></div>
<div id="prompt">Web Tool Name:</div><div id="answer"><input type="text" name="vnameu" id="vnameu" /></div>
<div id="prompt"><input type="submit" id="updatemain" name="updatemain" value="Update Information" /></div>
</fieldset>
</form>
</div>
</div>
</div>