I would recommend using jquery and will actually be using it to demonstrate…
html file…
<form name="form1" action="submit.php" method="post">
<tr bgcolor="#00BFFF">
<td><strong>Month</strong></td>
</tr>
<tr>
<td id='months'>
<select id='month' name="month">
<option value="january">January</option>
<option value="february">February</option>
<option value="march">March</option>
<option value="april">April</option>
<option value="may">May</option>
<option value="june">June</option>
<option value="july">July</option>
<option value="august">August</option>
<option value="september">September</option>
<option value="october">October</option>
<option value="november">November</option>
<option value="december">December</option>
</select>
</td>
<td id='days'></td>
<input type="hidden" name="pid" value="<?php echo $product_id ?>"/>
</tr>
<tr><td colspan="32" align="center"><input type="submit" value="SUBMIT DATA" name="submit" style="font-size:18px; font-weight:bold;" /></td></tr>
</form>
</table>
javascript file
$(document).ready(function(e)){
$('#month').change(function(e){
var month = $(this).val();
$.get('phpFileToGetRelativeValues.php?month=' + month, function(data){
if(data !== 'false'){
$('#days').append(data);
}
else {
alert('Something went wrong :(');
}
});
});
});
phpFileToGetRelativeValues.php file…
[php]
<?php
if(isset($_GET['month'])){
require 'dbConnection.php';
$month = $_GET['month'];
$sql = $link->query('SELECT * FROM table JOIN otherTable USING ('fk') WHERE month = "'.$month.'"');
if($sql){
$dayNumber = 1;
while($row = $sql->fetch_assoc()){
echo '
|
'
$dayNumber++;
}
}
else {
echo 'false';
}
}
[/php]
I'm not guaranteeing that this code will work (even if you change the values to your required specifications) but it is a good starting point. If you have questions about what's going on at any point please feel free to ask and I will do my best to explain / help you out with it.