根据PHP中的Dropdown表单选择更改变量的值

I am currently working with XML files in PHP and would like to be able to load in a specific XML file based on a selection from a dropdown list.

This is code I have been trying so far with help from some other stackoverflow posts about this method:

<html>
        <?php
        $submittedValue = "";
        $value0 = "Route 7602";
        $value1 = "Route 7603";

        if (isset($_POST["busroutes"])) {
            $submittedValue = $_POST["busroutes"];
        }
        ?>
        <form action="" name="busroutes" method="post">
        <select name="busroutes" onchange="this.form.submit()">
        <option value = "<?php echo $value0; ?>"<?php echo ($value0 == $submittedValue)?" SELECTED":""?>><?php echo $value0; ?></option>
        <option value = "<?php echo $value1; ?>"<?php echo ($value1 == $submittedValue)?" SELECTED":""?>><?php echo $value1; ?></option>
        </select>
        <noscript><input type="submit" value="Submit"></noscript>
        </form>

    <?php

        if($submittedValue = $value0){
        $urlbus = ("https://data.dublinked.ie/cgi-bin/rtpi/realtimebusinformation?stopid=7602&format=xml"); 
        }
        elseif($submittedValue = $value1){
        $urlbus = ("https://data.dublinked.ie/cgi-bin/rtpi/realtimebusinformation?stopid=7603&format=xml"); 
        }
        else{
            echo "No XML file loaded";
        }

        $dublinbus_array = simplexml_load_file($urlbus);

        echo '<pre>';
        print_r($dublinbus_array);
        echo '</pre>';
                ?>
                </html>

The first XML file with the stopid of 7602 is displaying correctly but the XML file with stopid of 7603 isn't. I have a feeling im close to something but just can't get over the line.

Any help would be greatly appreciated.

Use "===" for strict comparison not just "=" . Learn more details here http://www.programmerinterview.com/index.php/php-questions/difference-between-and-in-php/