select box

ok well ive done a script that basically echos all of the tables within my database into a combo box, the problem now is i want to validate it so if the user doesn't select a table then i want to echo that there wasn't no selection. i have made sure that i created a blank item within the select box aswel. here is my code.

<?php

$dbname = 'obso006_itemstock'; 
$sql = "SHOW TABLES FROM $dbname";
$result = mysql_query($sql);

if (!$result) {
    echo "DB Error, could not list tables\n";
    echo 'MySQL Error: ' . mysql_error();
    exit;
}
echo "<form method=\"post\" action=\"" . $_SERVER['PHP_SELF'] ."\">"; 
echo "<span class=\"style\">Please Select a Category:</span> &nbsp;&nbsp;&nbsp;<select name=\"dbtables\" id=\"dbtables\">\n";
echo "<option value=\"\"></option>";
while ($row = mysql_fetch_row($result)) {

	echo "<option value=\"".$row[0]."\">".$row[0]."</option>\n";

}

echo "<input type=\"submit\" name=\"select_table\" value=\"Submit\"></select></form>";

mysql_free_result($result);

?>

Code (markup):

 

$accept = array();
while ($row = mysql_fetch_row($result)) {

	echo "<option value=\"".$row[0]."\">".$row[0]."</option>\n";
	$accept[$row[0]] = true;
}

if(!isset($accept[$_POST['dbtables']])) { ... } else { ... }

PHP:

Faster than in_array.

 

<?php
if(empty($_POST['dbtables']))
{
echo 'Nothing is selected';
}
?>

PHP: