Error while getting select box value with php - php

Question

I am currently working on a project where a user chooses an option from a select box and submits a form, the form is then processed by PHP, and the PHP code determines what the select box value is, and does something based on that value.
My select box is called combined_group and has two select values: philharmonic_orchestra and symphony_orchestra.
This is how I am checking the selected value:
if($_POST['combined_group'] == "philharmonic_orchestra"){
$_SESSION['semesterprice'] = "170";
$_SESSION['fullprice'] = "330";
}
if($_POST['combined_group'] == "symphony_orchestra"){
$_SESSION['semesterprice'] = "275";
$_SESSION['fullprice'] = "530";
}
But when PHP runs through this code, neither if statement is chosen. I know that the value of $_POST['combined_group'] is, in fact, either of those two values, just PHP isn't picking it up for some reason.
Anybody care to help?
EDIT: My HTML form code is as follows
<select name="combined_group" class="OBJ-1">
<option value="" selected="">Select One</option>
<option value="philharmonic_orchestra">Philharmonic Orchestra</option>
<option value="symphony_orchestra ">Symphony Orchestra</option>
</select>

Answer 1

Client side
<select name="combined_group">
<option value="">Select an option</option>
<option value="philharmonic_orchestra">Philharmonic Orchestra</option>
<option value="symphony_orchestra">Symphony Orchestra</option>
</select>
Server side
if (! isset($_POST["combined_group"]))
{
exit('not set');
}
if (trim($_POST["combined_group"]) == '')
{
exit('not selected');
}
if (trim($_POST["combined_group"]) == 'philharmonic_orchestra')
{
//business logic for 'philharmonic_orchestra'
}
else
{
//business logic for 'symphony_orchestra'
}

Answer 2

Most likely is a bad HTML syntax. Check if your option item has value attribute:
<option value="...">...</option>

Answer 3

The reason why your conditional statement is failing, is because of a space in your option's value.
<option value="symphony_orchestra ">
^ right there
What you will need to do is remove it:
<option value="symphony_orchestra">
^ deleted space
Technical sidenote:
Had your conditional statement been:
if($_POST['combined_group'] == "symphony_orchestra ")
^ notice the space
with the space before the quote, it would have worked.
Anything between quotes is considered and part of an element's value.