how to sent data in multiple search options - php

Question

Hi guys i coded a search php in custom page for my site and want do search job in same page (i don't want send data to action page).
but i have problem i don't know why this is not work pleas can some one tell me what's problem and what is the current one?!
Thank you.
<div class="row-fluid">
<div class="page-header">
<h1>Search Users: </h1>
</div>
<center>
<h2>Find user(s)</h2>
<form name="search" method="post" action="">
Seach for: <input type="text" name="find" /> with
<Select NAME="field">
<Option VALUE="user_id">User ID</option>
<Option VALUE="username">Username</option>
<Option VALUE="serialnumber">SerialNumber</option>
<Option VALUE="ip_address">IP Address</option>
</Select>
<input type="hidden" name="searching" value="yes" />
<input type="submit" name="search" value="Search" class="btn btn-success" style="vertical-align: super;" />
</form>
<span><?php echo $error; ?></span>
</center>
<table class="table table-striped table-bordered table-condensed">
<thead>
<tr>
<th>ID</th>
<th>Name</th>
<th>E-mail</th>
<th>IP</th>
<th>serialnumber</th>
<th>Actions</th>
</tr>
</thead>
<?php
if (isset($_POST['submit'])) {
if (empty($_POST['find']) || empty($_POST['field'])) {
$error = "Pleas choice options";
}
else
{
$find=$_POST['find'];
$value=$_POST['field'];
$sql = "SELECT * FROM login_log WHERE '$value' = '$find'";
$result = $db->sql_query($sql);
while($row = $db->sql_fetchrow($result)) {
?>
<tbody>
<tr class="pending-user">
<td><?php echo $row['user_id']; ?></td>
<td><?php echo $row['username']; ?></td>
<td><?php echo $row['email']; ?></td>
<td><?php echo $row['ip_address']; ?></td>
<td><?php echo $row['serialnumber']; ?></td>
<td>Ban User</td>
</tr>
</tbody>
<?php
}
}
}
?>
</table>
</div>

Answer 1

$_POST will contain elements from the form where you use the name= attribute for your form fields. $_POST['submit'] won't exist unless you have name="submit" for one of the fields or buttons. Do a var_dump($_POST) to see what values are being sent back to the form.
Change isset($_POST['submit']) to isset($_POST['search']
See a tutorial on how to use forms.