<?php
 
$selected = $_POST['selected'];
 
if ($selected != "")
{
  // MySQL commands to retrieve the info depending on what was selected
}
 
?>
 
//Page Code Here
 
 
 
<form action="thispage.php" method="post" name="first_form">
 
<select name="first_select" onChange="document.first_form.submit();">
 
</form>
 
<form action="search.php" method="post" name="second_form">
 
<?php
 
//Use a for loop to go through the array of info recieved from the database and populate the second select field
 
?>
 
<input type="submit>
 
</form>