Q:

Ajax driven user group system that uses an HTML frontend with PHP/MYSQL

I am a newbie so please excuse my ignorance.
I am making an Ajax driven user contact group web application that stores contacts based on designated assigned groups. Once a user contact has been created users are able to select various contact groups via a drop down box. This then displays a summary of each of the users inside the selected group along with individual check boxes for each user contact. The user can then either select individual or multiple user contacts with these check-boxes resulting in a detailed description of the users (select * users contact_group = family). The user must be able to delete single or multiple contacts without a page refresh.
I am Having difficulty looping and displaying the contacts with the check-boxes and being able to delete multiple users simultaneously. Note I'm only using a single table.

A:

A couple of things here:
You can get just the checked boxes with a simple selector: 
var inputs = $(':checkbox:checked');

Generate the checkbox in your results loop:
<?php
while($row = mysql_fetch_array($result)) :
    ?>
    <tr>
        <td><input type="checkbox" name="delete[]" value="<?= $row['User_Id']; ?>" /></td>
        <td><?= $row['First_Name']; ?></td>
        <td><?= $row['Last_Name']; ?></td>
        <td><?= $row['Email_Address']; ?></td>
    </tr>
    <?php
endwhile;

Your delete handler is a simple WHERE..IN query at this point:
// NOTE: Use an abstraction library to sanitize user-submitted data for the query
$filtered_delete_ids = implode(',', $_POST['delete']);
$query = "DELETE FROM `users` WHERE `User_Id` IN (".$filtered_delete_ids.")";

