FAQ schema class

FAQ.class.php

<?php

class FAQ
{
  public $html = '';
  function __construct ( )
  {
    add_shortcode( 'sl9-faq', array( $this, 'shortcode' ) );
  }

  function shortcode ( $atts, $content=null )
  {
    $a = shortcode_atts( array(
      "question"    => ''
    ), $atts );

    $html .= '<article itemscope itemtype="http://schema.org/Question">';
    $html .= '<h3 itemprop="name">' .  sanitize_text_field($a['question']) . '</h3>';
    $html .= '<section itemprop="suggestedAnswer acceptedAnswer" itemscope itemtype="http://schema.org/Answer">';
    $html .= '<p itemprop="text">'. esc_html__($content) .'</p>';
    $html .= '</section>';
    $html .= '</article>';
    return $html;
  }
}

Timeline.class.php

<?php

/**
 * Summary: Timeline block will provide predictable timeline blocks with responsiveness.
 * 
 * Description: Shortcode Usage: 
 * PARENT: [sl9-tl class="my-class"]
 *   [sl9-tl-step class="my-other-class"]Content[/sl9-tl-step]
 * ENDPARENT: [/sl9-tl]
 */
require_once 'Shortcode.interface.php';

class TimelineStep implements ShortcodeInterface
{
  public function __construct( )
  {
    add_shortcode( 'sl9-tl', array( $this, 'shortcode_parent' ) );
    add_shortcode( 'sl9-tl-step', array( $this, 'shortcode' ) );
  }

  public function shortcode ( $atts, $content=null )
  {
    $a = shortcode_atts( array(
      'class' => ' ',
      'title' => '',
      'side' => ' left ',
      'step' => '',
      'image_id' => null
    ), $atts);
    

    $html .= '<div><div class="step-image step-clip-path-'. $a['side'] .' pull-'. self::sideReverse( $a['side'] ) .'">';
    if ( $a['image_id'] ) {
      $html .= do_shortcode( '[vc_single_image img_size="full" alignment="center" onclick="link_image" animation="animate-when-visible" css_animation="el-fade" image="'. $a['image_id'] .'"]' );
    }
    $html .= '</div>';

    $html .= '<div data-step="'. $a['step'] .'" class="step ' . $a['side'] . $a['class'] .'">';
    $html .= '<div class="tmc-step-content">';
    $html .= '<h3>'. $a['title'] .'</h3>';
    $html .= '<p>'. $content .'</p></div></div></div>';
    return $html;
  }

  public function shortcode_parent ( $atts, $content=null )
  {
    $a = shortcode_atts( array(
      'class' => ' ',
      'title' => '',
      'side' => ' left '
    ), $atts);
  
    $html = '<section class="tmc-steps">';
    $html .= do_shortcode($content);
    $html .= '</section>';
    return $html; 
  }

  protected static function sideReverse ( string $side )
  {
    switch ( $side ) {
      case 'left':
        return 'right';
        break;
      case 'right':
        return 'left';
        break;
      default:
        return 'Error: Please enter either "right" or "left" as a string.';
        break;
    }
  }
}