Php loop mysql result by year from date field

I’m getting data from the database and want to present the data by year.
Like this:

2013

Event A

Event B

2012

Event X

Event Y
Etc.

I’ve got this mysql query and PHP code which presents all the data in one list:

`SELECT * FROM table a
INNER JOIN posts b
ON a.event_id = b.ID
WHERE a.user_id = 14
ORDER BY a.event_date DESC

$results = $wpdb->get_results($query);

    if ($results) {
        echo '<h3>Title</h3>';
        echo '<ul>';
        foreach ($results as $row) {
            $event_id = $row->event_id;
            $rawDate = $row->event_date;
            $newDate = date("d-m-Y", strtotime($rawDate));

            echo '<li>' . $newDate . ': <a href="' . tribe_get_event_link($row->event_id) . '" target="_blank">' . $row->post_title . '</a> (' . $row->points . ' PE)</li>';
        }
        echo '</ul>';
    }
}`

So I like to get this data by year from the field event_date or $newDate which is a date field in Y-m-d H:i:s format, but I can’t get this done. I guess I need an extra foreach, but how?

Thanks in advance!

>Solution :

As CBroe commented, save the previous value and compare with the current value inside your loop:

    if ($results) {
        $pre = '';                                      // previous year
        foreach ($results as $row) {
            $current = date("Y", strtotime($row->event_date));
            if ($current != $pre) {
                echo '<h3>'.$current.'</h3>';          // output if year changed
                echo '<ul>';
            }


            $event_id = $row->event_id;
            $rawDate = $row->event_date;
            $newDate = date("d-m-Y", strtotime($rawDate));

            echo '<li>' . $newDate . ': <a href="' . tribe_get_event_link($row->event_id) . '" target="_blank">' . $row->post_title . '</a> (' . $row->points . ' PE)</li>';


            if ($current != $pre) {                  // output if year changed
                echo '</ul>';
                $pre = $current;                     // set new previous year
            }
        }
    }