Php mysql html form submission error - php

Question

I'm working on a cms for my site and this form is not submitting. I know its a query problem, but I can't figure out whats wrong. Any help? Also, the $db is in my config and I do include it at the top of the page. The problem is its not submitting and all it does it refresh, nothing else. I also want to display there form submissions in a table later, but I don't know how to do that, if anyone can help me with that part that would be great as well.
php:
<?php
if(isset($_POST['submit']))
{
$c_name = $_POST['channel_username'];
$v_link = $_POST['video_link'];
$v_title = $_POST['video_title'];
$v_desc = $_POST['vido_description'];
$v_tags = $_POST['video_tags'];
$m_sources = $_POST['music_sources'];
$s_requests = $_POST['special_requests'];
if(empty($c_name) or empty($v_link) or empty($v_title) or empty($v_title) or empty($v_desc) or empty($v_tags))
{
echo 'You must fill in the first 5 fields.';
}
else
{
$getRank = $db->query("SELECT * FROM users WHERE username = '".$_SESSION['username']."'");
while ($row = $getRank->fetch_assoc())
{
$usename = $row['username'];
$rank = $row['rank'];
}
$db->query("INSERT INTO submitted_forms (username, rank, channel_username, video_link, video_title, video_description, video_tags, music_sources, special_requests) VALUES ('$username', '$rank', '$c_name', '$v_link', '$v_title', '$v_desc', '$v_tags', '$m_sources', '$s_requests')");
echo 'Form submitted successfully.';
}
}
?>
Html:
<form method="POST">
<p>Channel name <input type="text" name="channel_name" required>*</p>
<p>Video Link <input type="text" name="video_link" required>*</p>
<p>Video Title <input type="text" name="video_title" required>*</p>
<p>Video Description <input type="text" name="video_description" required>*</p>
<p>Video Tags <input type="text" name="video_tags" required>*</p>
<p>Music Sources <input type="text" name="music_sources"></p>
<p>Special Requests <input type="text" name="special_requests"></p>
<br></br>
<p><input type="submit" name="submit" value="Submit"></p>
</form>

Answer 1

If the problem is indeed with the query, then it's probably this:
$db->query("INSERT INTO submitted_forms (username, rank, channel_username, video_link, video_title, video_description, video_tags, music_sources, special_requests) VALUES (''.$username.'', ''.$rank.'', ''.$c_name.'', ''.$v_link.'', ''.$v_title.'', ''.$v_desc.'', ''.$v_tags.'', ''.$m_sources.'', ''.$s_requests.'')");
I think instead, you want:
$db->query("INSERT INTO submitted_forms (username, rank, channel_username, video_link, video_title, video_description, video_tags, music_sources, special_requests) VALUES ('$username', '$rank', '$c_name', '$v_link', '$v_title', '$v_desc', '$v_tags', '$m_sources', '$s_requests')");
-- edit --
further to that, although it won't give you an error as-is, you really oughtn't insert fresh POST data in there. At the very least you probably want to use mysqli_real_escape_string on it.