Wordpress: add radio button to admin Users table

gistfile1.txt

/* 
 * Add a column to the Users table, with a radio button
 * The radio button updates a usermeta field via ajax
 */

add_filter( 'manage_users_columns', 'add_display_column');
function add_display_column( $columns){
    $columns['display_as'] = 'Display as';
    return $columns;
}

add_filter('manage_users_custom_column',  'add_display_value', 50, 3);	// we use a lower priority (higher number, 50) here so as to fire after the custom_metadata plugin, which interferes. Damn plugin
function add_display_value( $value, $column_name, $user_id ){
	$user = get_userdata( $user_id );
	switch ($column_name) {
		case 'display_as' :
			$buttons =  '<label><input type="radio" class="save_display" name="display_as-'.$user_id.'" value="team" '.checked( 'team' == $user->display_as, true, false ).'> Team member</label><br />'.
						'<label><input type="radio" class="save_display" name="display_as-'.$user_id.'" value="friend" '.checked( 'friend' == $user->display_as, true, false ).'> BFF</label>';
			return $buttons;
			break;
		default:
	}

	return $value;
}

add_action('wp_ajax_save_display_value', 'save_display_value');
function save_display_value(){
	$value = $_POST['value'];
	$user_id = $_POST['userid'];
	update_usermeta($user_id, 'display_as', $value );
	// echo 'success';
	exit();
}

add_action('admin_footer', 'save_display_value_javascript'); 
function save_display_value_javascript() {
	global $current_screen;
	if ($current_screen->id != 'users') return; ?>
	<script type="text/javascript">
		jQuery('.save_display').click(function() {
			var value = jQuery(this).val();
			var userid = jQuery(this).attr('name').split('-')[1];
			jQuery.post('<?php echo admin_url("admin-ajax.php") ?>', { action: 'save_display_value', userid: userid, value: value }, function( response ) { /* do nothing */ } );
		});
	</script>
	<?php
}