Extends Yoast schema data to add events

Schema_Event.php

<?php

use \Yoast\WP\SEO\Generators\Schema\Abstract_Schema_Piece;

class Schema_Event extends Abstract_Schema_Piece {

	/**
	 * Determines whether or not a piece should be added to the graph.
	 *
	 * @return bool
	 */
	public function is_needed() {
		if ( is_singular( 'event' ) ) {
			return true;
		}

		return false;
	}

	/**
	 * Adds our Event piece of the graph.
	 *
	 * @return array $graph Event Schema markup
	 */
	public function generate() {

		$wa_add_event_structured_data = get_post_meta( $this->context->id, 'wa_add_event_structured_data', true );
		if ( empty( $wa_add_event_structured_data ) ) {
			//No details added
			return false;
		}

		$data = $this->build_event_data();


		return $data;
	}

	/**
	 * Builds our array of Schema Event data for a given post ID.
	 *
	 * @return array An array of Schema Event data.
	 */
	protected function build_event_data() {

		$event_name              = get_post_meta( $this->context->id, 'wa_event_name', true );
		$wa_event_location       = get_post_meta( $this->context->id, 'wa_event_location', true );
		$wa_event_street_address = get_post_meta( $this->context->id, 'wa_event_street_address', true );
		$wa_event_locality       = get_post_meta( $this->context->id, 'wa_event_locality', true );
		$wa_event_zip            = get_post_meta( $this->context->id, 'wa_event_zip', true );
		$wa_event_region         = get_post_meta( $this->context->id, 'wa_event_region', true );
		$wa_event_country        = get_post_meta( $this->context->id, 'wa_event_country', true );
		$wa_event_start_date     = get_post_meta( $this->context->id, 'wa_event_start_date', true );
		$wa_event_end_date       = get_post_meta( $this->context->id, 'wa_event_end_date', true );
		$wa_event_description    = get_post_meta( $this->context->id, 'wa_event_description', true );
		$image                   = false;
		$has_featured_image      = has_post_thumbnail( $this->context->id );
		if ( $has_featured_image ) {
			$image = wp_prepare_attachment_for_js( get_post_thumbnail_id( $this->context->id ) );
		}

		$data = array(
			'@type'     => 'Event',
			'@id'       => $this->context->canonical . '#event',
			'name'      => $event_name,
			'startDate' => date( 'Y-m-d', strtotime( $wa_event_start_date ) ),
			'location'  => array(
				'@type'   => 'Place',
				'name'    => $wa_event_location,
				'address' => array(
					'@type'           => 'PostalAddress',
					"streetAddress"   => $wa_event_street_address,
					"addressLocality" => $wa_event_locality,
					"postalCode"      => $wa_event_zip,
					"addressRegion"   => $wa_event_region,
					"addressCountry"  => $wa_event_country
				)
			)
		);

		if ( $wa_event_end_date ) {
			$data['endDate'] = date( 'Y-m-d', strtotime( $wa_event_end_date ) );
		}

		if ( $wa_event_description ) {
			$data['description'] = $wa_event_description;
		}

		if ( $image ) {
			$data['image'] = array(
				'@type'  => 'ImageObject',
				'url'    => $image['url'],
				'height' => $image['height'],
				'width'  => $image['width']
			);
		}

		return $data;

	}

}