I would like to delete a row from mysql database. The row I would like to delete is the 'selected item' in the combobox.

My code so far:

    $sql = "SELECT data_id FROM projects";
    $result = mysql_query($sql);

    echo "<select name='data_id '>";
    echo "<option selected>Please select...</option>";
    while ($row = mysql_fetch_array($result))
    {
        echo "<option value='" . $row['data_id '] . "'>" . $row['data_id'] . "</option>";
    }
    echo "</select>";

    ?>
    <tr><td><input type="submit" name="delete" value="Delete" id="delete"></td></tr></tr></table>
    <?php
     //delete selected item from projects table...
    ?>

The combobox is showing all the items from my projects table. When I select an item, then click on 'delete' I would like to delete that item from the table.

Any help will be appreciated.

I did not get why do they suggest you to use ajax, while you can make simple form

<form method="post" action="">
<tr><td>
//SOME PHP where you obtain from the database the data_id (this you have done already)
    <option value='" . $row['data_id '] . "'>" . $row['data_id'] . "</option>
//
<input type="submit" name="delete" value="Delete" id="delete">
</td></tr>
</form>

and on same page at the top before HTML

<?php
if(isset($_POST['delete']) {
//and now mysql DELETE FROM .... WHERE id = $_POST['data_id']
//dont forget to escape and use mysli instead of mysql
}
?>

Btw. dont use mysql_* its deprecated, + escape everything in mysql + dont use fetch_array when you dont need an array, fetch_assoc is fine ;) Hope that helps.