PHP dynamic population problem

I'm brand new with PHP and have been thrown into the pool with no swimming lessons, so I appreciate the tutorials!

I am trying to populate a second dropdown with database values based on the first one. I have a couple problems, but let me deal with the first one:

This is on a Wordpress site; WP is changing names for the site by stripping extensions and adding a trailing "/". For example, my page is named state_selection.php. Wordpress turns the address to /state-selection/.

When I reload the page on the form reload, my value is like this: /state-selection/?state=VA. It comes back as Error 404.

I know I have other issues since the Submit button doesn't show on the first load of the page. Here is my code:

The JS script is in the header.php file:
<SCRIPT language=JavaScript>
function reload(form){
var val=form.state.options[form.state.options.selectedIndex].value;
self.location='state_selection.php?state=' + val ;
}
</script>

I have tried
self.location='state-selection/?state=' + val ;

But I still get the Error 404.

Is there any way to pass the state value without a reload form?

BTW, I have done the state select as an array, and when that didn't work, I did a straight HTML box. I abbreviated it here for sake of space.

Here is the main page code:
<?php /* Template Name: State and Employer Selection*/ ?>

<?php get_header(); ?>

<div id="main_content">
<div class="stateemp">
<p>PLEASE SELECT YOUR STATE IN THE DROP DOWN BOX BELOW:</p>
<br /><br />
<form action="state_selection.php" method="post" name="state">
<select name="state" onchange="reload(this.form)">
<option value="" selected="selected">Select state</option>
<option value="AL">Alabama</option>
<option value="AK">Alaska</option>
<option value="AZ">Arizona</option>
<option value="AR">Arkansas</option>
<option value="CA">California</option>
<option value="CO">Colorado</option>
</select>

<br /><br />

<p>PLEASE SELECT YOUR EMPLOYER'S NAME:</p>

<select name='employer'>
<option value=''>Choose Employer</option>

<?php

// set database server access variables:
$host = "localhost";
$user = "";
$pass = "";
$db = "";

// open connection
$connection = mysql_connect($host, $user, $pass) or die ("Unable to connect!");

// select database
mysql_select_db($db) or die ("Unable to select database!");

$state=$_GET['state'];

// create query
if(isset($state) and strlen($state) > 0){
$quer=mysql_query("SELECT distinct name FROM employer_state state=$state order by name");
}else
{$quer=mysql_query("SELECT distinct name order by name"); }

// execute query
$result = mysql_query($query) or die ("<p>Error in query: $query. ".mysql_error());

// printing the list box select command

while($nt=mysql_fetch_array($result)){//Array or records stored in $nt
echo "<option value=$nt[id]>$nt[name]</option>";
}


// close connection
mysql_close($connection);


?>

</select>
<br /><br />
<input type="submit" name="mysubmit" value="Submit Form" />
</form>
</div>
</div>

<?php get_sidebar(); ?>
<?php get_footer(); ?>


THank you for your help!