Plugin works great once fixed

Once I replace add_swpm_fields with:

[ Moderator note: code fixed. Please wrap code in the backtick character or use the code button. ]

function add_swpm_fields( $id, $item, $depth, $args ) {

                //// Logged levels
                $levels = $this->get_membership_levels();

                $item_groups = get_post_meta( $item->ID, self::META_KEY_NAME, true );

                ?>
                    <p class="description description-wide menu-item-actions">
                        Membership groups permitted :
                        <?php foreach($levels as $level)
                        {
                            $key = self::META_KEY_NAME.'-'.$level->id;
                            $name  = sprintf( '%s[%s]', $key, $item->ID );
			    // Handle the case where there is no array because it is a new menu item that has been added.
			    // In this case checkall of the member levels since it is more likely to be included than not.
			    if ( is_array( $item_groups ) ) {
				$checked = in_array($level->id, $item_groups) || (count($item_groups) == 0 && $level->id == self::NOT_LOGGED_IN_LEVEL_ID) ? "checked" : "";
			    } else {
				$checked = "checked";
                            }

			    // If the class menu-item-title is used then this is perceived to be a menu item that can be moved and will cause the
			    // Under link to include all of the member leves. Not good.
                            ?>
                            <label class="swpm-menu-item-title" style="padding-top:8px;padding-bottom:8px;">
                               <?php printf(
                                 '<input type="checkbox" class="menu-item-checkbox" name="%3$s" value="%1$s" %4$s> %2$s',
                                 $level->id,
                                 $level->alias,
                                 $name,
                                 $checked); ?>
                            </label>
                        <?php } ?>
                    </p>
                <?php
            }

it works well.