Customize shortcode of post_meta_infos to display the last modified date

Hello,
I’m using the ALB for my plog posts. To display the post’s meta infos I created a file named post_meta_infos.php and loaded it into the avia-shortcodes folder. So I can use the shortcode to display meta infos and it works fine. I found the code for the post_meta_infos.php in the forums here. Unfortunately the code does not contain any commands to display the last modified date of the post entry. Therefore I need some additions for The code. I tried by myself, but couldn’t get it work for I have no real php-programming-skills. Could you help?
Here is the code (without last modified date) I use.

<?php
/**
 * Comments Element
 * Adds a comment form to the page
 */
 
// Don't load directly
if ( !defined('ABSPATH') ) { die('-1'); }

if ( !class_exists( 'avia_post_meta_info' ) )
{
	class avia_post_meta_info extends aviaShortcodeTemplate{
			
			/**
			 * Create the config array for the shortcode button
			 */
			function shortcode_insert_button()
			{
				$this->config['name']		= __('Post Meta', 'avia_framework' );
				$this->config['tab']		= __('Content Elements', 'avia_framework' );
				$this->config['icon']		= AviaBuilder::$path['imagesURL']."sc-comments.png";
				$this->config['order']		= 28;
				$this->config['target']		= 'avia-target-insert';
				$this->config['shortcode'] 	= 'av_post_meta';
                $this->config['tinyMCE'] 	= array('disable' => "true");
				$this->config['tooltip'] 	= __('Add the post meta infos', 'avia_framework' );
                //$this->config['drag-level'] = 1;
			}
			

			 
			/**
			 * Editor Element - this function defines the visual appearance of an element on the AviaBuilder Canvas
			 * Most common usage is to define some markup in the $params['innerHtml'] which is then inserted into the drag and drop container
			 * Less often used: $params['data'] to add data attributes, $params['class'] to modify the className
			 *
			 *
			 * @param array $params this array holds the default values for $content and $args. 
			 * @return $params the return array usually holds an innerHtml key that holds item specific markup.
			 */
            function editor_element($params)
            {
                $params['innerHtml'] = "<img src='".$this->config['icon']."' title='".$this->config['name']."' />";
                $params['innerHtml'].= "<div class='avia-element-label'>".$this->config['name']."</div>";
                $params['content'] 	 = NULL; //remove to allow content elements
                return $params;
            }
			
			/**
			 * Frontend Shortcode Handler
			 *
			 * @param array $atts array of attributes
			 * @param string $content text within enclosing form of shortcode element 
			 * @param string $shortcodename the shortcode found, when == callback name
			 * @return string $output returns the modified html string 
			 */
			function shortcode_handler($atts, $content = "", $shortcodename = "", $meta = "")
			{
				$the_id = get_the_ID();
				
				$output  = '<header class="entry-content-header">';
                $output .= "<span class='post-meta-infos'>";
                $markup  = avia_markup_helper(array('context' => 'entry_time','echo'=>false));
                $output .= '<time class="date-container minor-meta updated" {$markup}>'.get_the_time(get_option('date_format'))."</time>";
                $output .= "<span class='text-sep text-sep-date'>/</span>";

                    if ( get_comments_number() != "0" || comments_open() ){

                    $output .= "<span class='comment-container minor-meta'>";
					ob_start();
					comments_popup_link(  "0 ".__('Comments','avia_framework'),
                                          "1 ".__('Comment' ,'avia_framework'),
                                          "% ".__('Comments','avia_framework'),'comments-link',
                                          "".__('Comments Disabled','avia_framework'));
										  $comment = ob_get_clean(); 
										  $output .= $comment;
                    $output .= "</span>";
                    $output .= "<span class='text-sep text-sep-comment'>/</span>";
                    }

                    $taxonomies  = get_object_taxonomies(get_post_type($the_id));
                    $cats = '';
                    $excluded_taxonomies =  apply_filters('avf_exclude_taxonomies', array('post_tag','post_format'), get_post_type($the_id), $the_id);

                    if(!empty($taxonomies))
                    {
                        foreach($taxonomies as $taxonomy)
                        {
                            if(!in_array($taxonomy, $excluded_taxonomies))
                            {
                                $cats .= get_the_term_list($the_id, $taxonomy, '', ', ','').' ';
                            }
                        }
                    }

                    if(!empty($cats))
                    {
                        $output .= '<span class="blog-categories minor-meta">'.__('in','avia_framework')." ";
                        $output .= $cats;
                        $output .= '</span><span class="text-sep text-sep-cat">/</span>';
                    }

                    $output .= '<span class="blog-author minor-meta">'.__('by','avia_framework')." ";
					$markup  = avia_markup_helper(array('context' => 'author_name', 'echo'=>false));
                    $output .= '<span class="entry-author-link" $markup>';
                    $output .= '<span class="vcard author"><span class="fn">';
					ob_start();
					the_author_posts_link();
					$author  = ob_get_clean(); 
                    $output .= $author;
                    $output .= '</span></span>';
                    $output .= '</span>';
                    $output .= '</span>';
                $output .= '</span>';
				$output .= '</header>';
				
				
        		return $output;
        	}		
			
	}
}

I tried this: …

 $output .= '<time class="date-container minor-meta updated" {$markup}>'.get_the_time(get_option('date_format'))."</time>";
                $output .= "<span class='text-sep text-sep-date'>/</span>";
				
				
				
					if (the_modified_date('d.m.Y') != the_date('d.m.Y')) {
					
					$output .= '<time class="date-container minor-meta updated">'.the_modified_date('d.m.Y')."</time>";
					$output .= "<span class='text-sep text-sep-date'>/</span>";					
					}
						
		
				
                    if ( get_comments_number() != "0" || comments_open() ){

                    $output .= "<span class='comment-container minor-meta'>";
					ob_start();

Didn’t work.

Best regards,
lebenspraxis