assign statement to drop down list PHP - php

Question

I asked this question previously but i think i made it too complex, I want to assign a query if a value from a list is selected.
<form id="filter" name="filter" method="post" action="">
<select>
<option value="petrol">Petrol</option>
<option value="diesel">Diesel</option>
</select>
<p><input name="filter" type="button" value="Filter" /></p>
</form>
What i want to achieve is if user selects petrol the run the following query
$query = mysql_query("SELECT fuel_type from car WHERE fuel_type = 'petrol'");

Answer 1

<form id="filter" name="filter" method="post" action="">
<select id="college" name="fuel" onchange="changeValue();">
<option value="petrol">Petrol</option>
<option value="diesel">Diesel</option>
</select>
<p><input name="filter" type="button" value="Filter" /></p>
</form>
If you want to post the value in form submit use like this
$ctext = $_POST['fuel'];
$list = mysql_query("SELECT fuel_type from car WHERE fuel_type ='$ctext'");
$row = mysql_fetch_array($list);
//process $row
If you don't want to submit the form, you can use jquery in onchange event...
js code
<script type="text/javascript" src="jquery.js"></script>
<script type="text/javascript">
function changeValue() {
var ctext = $("#college option:selected").val();
$.ajax({ url: "yourfile.php",
data: {"ctext":ctext},
type: 'post',
success: function(output) {
//display output here
}
});
}
yourfile.php
<?php
//connect to db
$ctext = $_POST['ctext'];
$list = mysql_query("SELECT fuel_type from car WHERE fuel_type ='$ctext'");
$row = mysql_fetch_array($list);
echo $row['fuel_type'];
?>

Answer 2

Give your select tag a name:
<select name="fuel">
<option value="petrol">Petrol</option>
<option value="diesel">Diesel</option>
</select>
Then in your PHP you can do something simple like:
<?php
if(isset($_POST['cmdFilter']))
{
echo "You selected the fuel type: " . $_POST['fuel'];
}
?>
You can also set the select to have an id instead and use JQuery to send an ajax request passing it the value by giving selecting it by $("#myIdforSelect").val()
P.S
Be sure to sanitise your input ;)

Answer 3

Although I would also suggest the AJAX method, I just want to make it clear that you do not HAVE to use AJAX to accomplish this.
If your filter options are not too complex or many, then you can simply do a pull for all available options for any level of the filter tree on load and hide them initially. Then, as the user drills down into each section, you show them the next one accordingly (via javscript). In the end you can just submit a regular form with all the selected form fields via GET or POST.
This can effectively save bandwidth by running less calls to the server also :)
BUT if your choice tree gets too complicated, it might be better to just run AJAX request on user interaction.