Event Meta

class events_meta_box {

	public function __construct() {

		if ( is_admin() ) {
			add_action( 'load-post.php',     array( $this, 'init_metabox' ) );
			add_action( 'load-post-new.php', array( $this, 'init_metabox' ) );
		}

	}

	public function init_metabox() {

		add_action( 'add_meta_boxes',        array( $this, 'add_metabox' )         );
		add_action( 'save_post',             array( $this, 'save_metabox' ), 10, 2 );

	}

	public function add_metabox() {

		add_meta_box(
			'event_meta',
			'Event Detail',
			array( $this, 'render_metabox' ),
			'events',
			'advanced',
			'core'
		);

	}

	public function render_metabox( $post ) {

		// Retrieve an existing value from the database.
		$event_killdate = get_post_meta( $post->ID, 'event_killdate', true );
		$event_time = get_post_meta( $post->ID, 'event_time', true );
		$event_location = get_post_meta( $post->ID, 'event_location', true );

		// Set default values.
		if( empty( $event_killdate ) ) $event_killdate = '';
		if( empty( $event_time ) ) $event_time = '';
		if( empty( $event_location ) ) $event_location = '';

		// Form fields.
		echo '<table class="form-table">';

		echo '	<tr>';
		echo '		<th><label for="event_killdate" class="event_killdate_label">' . 'Display Until' . '</label></th>';
		echo '		<td>';
		echo '			<input type="date" id="event_killdate" name="event_killdate" class="event_killdate_field" placeholder="' . '' . '" value="' . esc_attr__( $event_killdate ) . '">';
		echo '			<p class="description">' . 'Enter the date to display the event as upcoming until' . '</p>';
		echo '		</td>';
		echo '	</tr>';

		echo '	<tr>';
		echo '		<th><label for="event_time" class="event_time_label">' . 'Enter the Time of the Event' . '</label></th>';
		echo '		<td>';
		echo '			<input type="text" id="event_time" name="event_time" class="event_time_field" placeholder="' . 'Enter the time' . '" value="' . esc_attr__( $event_time ) . '">';
		echo '		</td>';
		echo '	</tr>';

		echo '	<tr>';
		echo '		<th><label for="event_location" class="event_location_label">' . 'Event Location' . '</label></th>';
		echo '		<td>';
		echo '			<input type="text" id="event_location" name="event_location" class="event_location_field" placeholder="' . '' . '" value="' . esc_attr__( $event_location ) . '">';
		echo '			<p class="description">' . 'Where is this happening?' . '</p>';
		echo '		</td>';
		echo '	</tr>';

		echo '</table>';

	}

	public function save_metabox( $post_id, $post ) {

		// Sanitize user input.
		$event_new_killdate = isset( $_POST[ 'event_killdate' ] ) ? sanitize_text_field( $_POST[ 'event_killdate' ] ) : '';
		$event_new_time = isset( $_POST[ 'event_time' ] ) ? sanitize_text_field( $_POST[ 'event_time' ] ) : '';
		$event_new_location = isset( $_POST[ 'event_location' ] ) ? sanitize_text_field( $_POST[ 'event_location' ] ) : '';

		// Update the meta field in the database.
		update_post_meta( $post_id, 'event_killdate', $event_new_killdate );
		update_post_meta( $post_id, 'event_time', $event_new_time );
		update_post_meta( $post_id, 'event_location', $event_new_location );

	}

}

new events_meta_box;