Use dropdown list selection as mySQL query parameter - php

Question

I had asked a similar question a few days ago but think I was trying to do to much at one time. I am hoping someone can help get me started on this.
I have two drop down lists, one will be populated with years (2012, 2011 etc) and I have some mySQL databases called "db_2012", "db_2011" etc. In these databases are tables representing months.
I would like the user to select a year and then use that selection to query the correct db and return a list of table names which will be used to populate the second drop down list. Then click a button "See Results" to query the selected table and show the results.
I am putting this on a wordpress website and am using a php template file that I created. This is still new to me and what I have so far doesnt work like I want it too, it is basically setup now that you select a year and select a month (not populated from db) and click a button. It makes the query and my table is displayed, but I need this solution to be more dynamic and work as described above. Thanks for the help.
echo '<form action="" method="post">';
echo'<select name="years" id="years">';
foreach($yearList as $year){
echo'<option value="'.$year.'">'.$year.'</option>';
}
echo'</select><br />';
echo '<select name="monthList" id="months">';
foreach($monthList as $month) {
echo'<option value="'.$month.'">'.$month.'</option>';
}
echo '</select>';
echo '<input type=\'submit\' value=\'See Results\'>';
echo '</form'>
$yearList and $monthList are just pre populated arrays. So now from here I want to click the See Results button and query my sql database using the parameters from the drop down selections.
$database = $_POST['yearList'];
$month = $_POST['monthList'];
$wpdbtest_otherdb = new wpdb('Username', 'Password', $database, 'localhost');
$qStr = "SELECT * FROM $month";
$myResults = $wpdbtest_otherdb->get_results($qStr, OBJECT);

Answer 1

It sounds like you want to send an AJAX call to a separate php page for security and processing, then have the PHP return XML that you parse back into the second selection box via the AJAX callback. It can be a little messy, but it allows you to check for weird form values that users might inject.
Edit: The PHP will receive your AJAX parameters as parts of the $_GET or the $_POST array. From there, you can do your checks and db call (or not), then add header("Content-Type:text/xml"); so the server sends it back with the correct header. After that you'll need to echo the XML-formatted data you want the JavaScript to receive. Just remember not to echo anything other than the XML if the request is supposed to go through.