Update mysql table using POST method - php

Question

I have a form with some textbox that loads the data from the database. I have created also a button where I can update the data but currently it's not working and I don't have any clue why.
Here's my query:
<?php
include('connect.php');
if (isset($_POST['btnUpdate'])){
$query = "UPDATE users SET fname = '".$_POST['fname']."', lname = '".$_POST['lname']."' WHERE user_id = '".$_POST['id']."'";
$result = mysql_query($query);
if ($result) {
die("<strong>Updated</strong>");
} else {
die("<strong>Error ".mysql_error()."</strong>");
}
}
?>
Here's my form:
<form class="form-horizontal" role="form" action="" method="post">
<input type="hidden" name="id" value="<?php echo $row['user_id']; ?>"/>
<div class="form-group">
<label class="col-lg-3 control-label">First name:</label>
<div class="col-lg-8">
<input class="form-control" name="fname" type="text" value="<?php echo $row['fname'];?>">
</div>
<label class="col-lg-3 control-label">Last name:</label>
<div class="col-lg-8">
<input class="form-control" name="lname" type="text" value="<?php echo $row['lname'];?>">
</div>
<label class="col-md-3 control-label"></label>
<div class="col-md-8" >
<input type="button" name="btnUpdate" class="btn btn-primary" value="Save Changes">
<span></span>
<input type="reset" class="btn btn-default" value="Cancel">
</div>
</div>
</form>
I've tried everything but it won't update my database. It doesn't have any error whatsoever when I checked it on the browser. I'm running out of ideas. Anyone know what part of my code is wrong? I'm still a beginner to php and I cannot seem to understand what's wrong here. Any ideas how to solve this problem would be greatly appreciated. Thanks

Answer 1

Posting as a community wiki; I feel no rep should come of it.
<input type="button"> does not by default propagate POST. Therefore you either need to use a "submit" type:
Either <input type="submit"> or <button type="submit">.
References:
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input/button
type
The type of the button. Possible values are:
submit: The button submits the form data to the server. This is the default if the attribute is not specified, or if the attribute is dynamically changed to an empty or invalid value.
reset: The button resets all the controls to their initial values.
button: The button has no default behavior. It can have client-side scripts associated with the element's events, which are triggered when the events occur.
You're also open to a serious SQL injection if your site is live or intended to go live.
You should start looking into switching over to either the mysqli_ or PDO api and with a prepared statement.
References:
http://php.net/manual/en/mysqli.prepare.php
http://php.net/manual/en/pdo.prepared-statements.php
https://en.wikipedia.org/wiki/SQL_injection