PHP中的$输出社交按钮

Question

First of all I'm not even sure the appropriate title for this post, I'm just trying adding social buttons class in php file but it doesn't work or giving syntax error. Here are the codes where i want to social code.

This is actually a portfolio when you click over image it zoomout and i want to show social icons to share image..

code

if (!function_exists('photoswipe_wrapper')) {
function photoswipe_wrapper( $atts ) { 
    echo '  
        <div id="gallery" class="pswp" tabindex="-1" role="dialog" aria-hidden="true">
            <div class="pswp__bg"></div>

            <div class="pswp__scroll-wrap">

              <div class="pswp__container">
                <div class="pswp__item"></div>
                <div class="pswp__item"></div>
                <div class="pswp__item"></div>
              </div>

              <div class="pswp__ui pswp__ui--hidden">

                <div class="pswp__top-bar">

                    <div class="pswp__counter"></div>

                    <button class="pswp__button pswp__button--close" title="Close (Esc)"></button>

                    <button class="pswp__button pswp__button--share" title="Share"></button>

                    <button class="pswp__button pswp__button--fs" title="Toggle fullscreen"></button>

                    <button class="pswp__button pswp__button--zoom" title="Zoom in/out"></button>

                    <div class="pswp__preloader">
                        <div class="pswp__preloader__icn">
                          <div class="pswp__preloader__cut">
                            <div class="pswp__preloader__donut"></div>
                          </div>
                        </div>
                    </div>
                </div>


                <!-- <div class="pswp__loading-indicator"><div class="pswp__loading-indicator__line"></div></div> -->

                <div class="pswp__share-modal pswp__share-modal--hidden pswp__single-tap">
                    <div class="pswp__share-tooltip">
                        <!-- <a href="#" class="pswp__share--facebook"></a>
                        <a href="#" class="pswp__share--twitter"></a>
                        <a href="#" class="pswp__share--pinterest"></a>
                        <a href="#" download class="pswp__share--download"></a> -->
                    </div>
                </div>

                <button class="pswp__button pswp__button--arrow--left" title="Previous (arrow left)"></button>
                <button class="pswp__button pswp__button--arrow--right" title="Next (arrow right)"></button>
                <div class="pswp__caption">     

                  <div class="pswp__caption__center">
                  </div>
                </div>
              </div>

            </div>

        </div>' ;

}
add_action('wp_footer','photoswipe_wrapper');
}

This is the social codes i want to add in above code

$output .= '<div class="gallery-side-heading-wrap portfolio-share clearfix"><h6 class="gallery-side-heading">'.__('Share This', 'be-themes').'</h6>';
        $output .= '<p>';
        $output .= be_get_share_button(get_permalink($post->ID), get_the_title($post->ID) , $post->ID);
        $output .= '</p></div>';