how to display the selected value from combo box in php - php

Question

I have select (combo boxes) in PHP and after one was selected i fill the second one with data from the database.
the question is how to display my selection from the first combo box after the page reload.
I have the following code:
<select name="category" id="category" maxlength="30" onchange="this.form.submit();">
<option value =""></option>
<?php
require_once("config.php");
// Connect to server
$con = mysql_connect($ServerAddress,$ServerUser,$ServerPassword);
//choose DB
mysql_select_db($DbName, $con);
$sql = "SELECT * FROM `category` ORDER BY `name`";
$res = mysql_query($sql);
while ($row1 = mysql_fetch_array($res)){
echo '<option value ="'.$row1['name'].'">'.$row1['name'].'</option>';
}
?>
</select>
</span>
<label>race:</label>
<span>
<select name="race" id="race" maxlength="30" >
<option value =""></option>
<?php
if (isset($_POST['category'])) {
$var = $_POST['category'];
// Connect to server
$con = mysql_connect($ServerAddress,$ServerUser,$ServerPassword);
//choose DB
mysql_select_db($DbName, $con);
$sql = "SELECT * FROM `race` WHERE `category`='" . sqlSecure($var) . "'ORDER BY `race`";
$res = mysql_query($sql);
while ($row1 = mysql_fetch_array($res)){
echo '<option value ="'.$row1['race'].'">'.$row1['race'].'</option>';
}
}
?>
</select>

Answer 1

Method how to get values are defined in form tag in attribute method
In your case you need to get echo $_POST['category'] and compare it with name of option
Your code are not perfect. Look follows: :)
<?php
require_once("config.php");
// Connect to server
$con = mysql_connect($ServerAddress, $ServerUser, $ServerPassword);
//choose DB
mysql_select_db($DbName, $con);
?>
<select name="category" id="category" maxlength="30" onchange="this.form.submit();">
<option value=""></option>
<?php
$val = $_POST['category']?:'';
$sql = "SELECT * FROM `category` ORDER BY `name`";
$res = mysql_query($sql);
while ($row1 = mysql_fetch_array($res)) {
$selected = ($val == $row1['name'] ? 'selected="selected"' : '');
echo '<option value ="' . $row1['name'] . '" '. $selected .'>' . $row1['name'] . '</option>';
}
?>
</select>
</span>
<label>race:</label>
<span>
<select name="race" id="race" maxlength="30">
<option value=""></option>
<?php
if (isset($_POST['category'])) {
$var = $_POST['category'];
$sql = "SELECT * FROM `race` WHERE `category`='" . sqlSecure($var) . "'ORDER BY `race`";
$res = mysql_query($sql);
while ($row1 = mysql_fetch_array($res)) {
echo '<option value ="' . $row1['race'] . '">' . $row1['race'] . '</option>';
}
}
?>
</select>