在AJAX中使用GET方法

Question

I have a PHP form which has a field called "Travelling from:". This field is a drop-down box which has 4 options (routes) to choose from.

The HTML for this field is as follows;

<form id="bookingform" action="http://www.example.com/wp-content/themes/theme1/ajax-getvalues.php" method="get"> 
    <p>
        <b>Travelling from:</b><br>
        <select name="from" id="from" style="-webkit-appearance: menulist-button; width: 300px; position: absolute; height: 30px; font-size: 13px; padding: 5px;">
            <option value="">Select a Route...</option>
            <?php
            while ($row= mysqli_fetch_array($route)) {
                echo "<option value='". $row['Route'] ."'>" . 
                          $row['Route'] . 
                     "</option>";
            }
            ?>
        </select>
    </p><br><br>
</form>

Within the the head section of this file, I have the following code which listens for the select list change and makes the AJAX call;

 <script type="text/javascript">
 $(document).ready(function($) {
     var route_id = 'from'; //Route ID
     $('#'+route_id).change(function(e) {
         //Grab the chosen value on route change
         var selectroute = $(this).val();
         $.ajax({
             url: 'http://www.example.com/wp-content/themes/theme1/ajax-getvalues.php?from='+ encodeURIComponent(selectroute),
             success: function(data) {
                 alert(data);
             },
             error: function (xhr, ajaxOptions, thrownError) {
                 alert(xhr.status + " "+ thrownError);
             }
         });
     });
 });
 </script>

The alert in the above code appears with the selected value from the dropdown box as expected - which adds to my confusion.

And finally, the PHP file (ajax-getvalues.php) has the following code to receive the value;

Yet $selectroute seems to be empty.

I used the following code in the PHP file to test if $select route was empty;

<?php
$connection = mysqli_connect("localhost", "user", "password", "dbname");

$selectroute = mysqli_real_escape_string($connection, $_GET['from']);
if  ($selectroute != "") {
    $result = mysqli_query($connection, "SELECT DATE_FORMAT(SailingTime,'%h:%i %p') AS FormattedTime FROM wp_timetable WHERE Route_ID = 1 AND '$selectvalue' BETWEEN StartDate AND EndDate");
}
echo '<option value="">Please select a time...</option>';

while($row = mysqli_fetch_array($result))
{
    echo '<option value="'.$row['FormattedTime'].'">' . $row['FormattedTime'] . "</option>";
    echo $row['FormattedTime'] ."<br/>";
}

mysqli_free_result($result);
mysqli_close($connection);

Basically, results are produced in another drop-down on the form if $selectroute is not empty. But the results are not produced - therefore $selectroute is empty.

Answer 1

The problem is two fold in your success callback function selectroute is just the value of your form element.

var url = 'http://www.example.com/wp-content/themes/theme1/ajax-getvalues.php';
$.ajax({
    url: url + '?from=' + encodeURIComponent(selectroute),
    success: function(data) {
        alert(data);
        // I think you want to append the ajax response to the form.
        $('#bookingform').append($(data));
    },
    error: function (xhr, ajaxOptions, thrownError) {
        alert(xhr.status + " "+ thrownError);
    }
});

Also in your PHP script you don't seam to be doing anything with $selectroute and there is an uninitialized variable $selectvalue

<?php
$connection = mysqli_connect("localhost", "user", "password", "dbname");

$selectroute = mysqli_real_escape_string($connection, $_GET['from']);

// initialize $selectvalue to today date
$selectvalue = '2015-03-12';

$query = "SELECT DATE_FORMAT(SailingTime,'%h:%i %p') AS FormattedTime
          FROM wp_timetable
          WHERE Route_ID = 1 
          AND '$selectvalue' BETWEEN StartDate AND EndDate";

if  ($selectroute != "") {
    $result = mysqli_query($connection, $query);

    if ($result) {
        echo '<select>';
        echo '<option value="">Please select a time...</option>';

        while($row = mysqli_fetch_array($result)) {
            echo '<option value="'.$row['FormattedTime'].'">' .
                      $row['FormattedTime'] . 
                 '</option>';
        }
        echo '</select>';
        mysqli_free_result($result);
    }
}

mysqli_close($connection); 

?>