Demonstrates how to create a Participants Database form element that displays an iframe

pdb-iframe-element.php

<?php
/**
 * Plugin Name: PDB Iframe Form Element
 * Description: Demonstrates how to create a Participants Database form element that displays an iframe
 * 
 */

add_filter( 'pdb-set_form_element_types', 'pdb_iframe_register_element' );
add_action( 'pdb-form_element_build_iframe','pdb_iframe_element_building_function');
add_filter( 'pdb-before_display_form_element','pdb_iframe_element_value_display_function', 10, 2);

/**
 * adds the form element to the list of form elements
 * 
 * @param array $elements
 * @return array
 */
function pdb_iframe_register_element( $elements )
{
  $elements['iframe'] = 'Iframe';
  return $elements;
}

/**
 * supplies the form element HTML
 *
 * @param PDb_FormElement $field
 * @return null
 */
function pdb_iframe_element_building_function( $field )
{
  /* 
   * all we need to do here is set it as a text line element so the 
   * src value can be set
   */
  $field->form_element = 'text-line';
}

/**
 * shows the value of the array
 *
 * @param array $value the raw value of the field
 * @param PDb_Field_Item object $field
 * @return string HTML
 */
function pdb_iframe_element_value_display_function( $value, $field )
{
  if ( $field->form_element === 'iframe' ) {
    
    // if there is no src defined or the src value is invalid, show nothing
    if ( ! $field->has_content() ) {
      return '';
    }
    
    $value = '
<div class="pdb-iframe-container ' . $field->name . '-iframe">
  <iframe ' . pdb_iframe_html_attributes( $field->attributes() ) . ' src="' . esc_attr( $field->value() ) . '" ></iframe>
</div>
';
  }
  return $value;
}

/**
 * converts the attributes array into HTML attributes
 * 
 * @param array $atts
 * @return string the HTML attributes
 */
function pdb_iframe_html_attributes( $atts )
{
  $atts_html = '';
  
  // defines a list of allowed attributes
  $safe_atts = array(
      'align',
      'frameborder',
      'height',
      'longdesc',
      'marginheight',
      'marginwidth',
      'name',
      'sandbox',
      'scrolling',
      'width',
      'allowfullscreen',
      'style',
  );
  
  // this assembles the attributes into a valid attributes string
  foreach ( $atts as $attribute => $value ) {
    if ( in_array( $attribute, $safe_atts ) ) {
      $atts_html .= ' ' . esc_attr( $attribute ) . '="' . esc_attr( $value ) . '"';
    }
  }
  return $atts_html;
}