MetaBox – Certificate

class mb_certificate {

	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(
			'certificate_details',
			__( 'Zertifikate', 'text_domain' ),
			array( $this, 'render_metabox' ),
			'pt_certificate',
			'advanced',
			'default'
		);

	}

	public function render_metabox( $post ) {

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

		// Set default values.
		if( empty( $certificate_url ) ) $certificate_url = '';
		if( empty( $certificate_runtime ) ) $certificate_runtime = '';

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

		echo '	<tr>';
		echo '		<th><label for="certificate_url" class="certificate_url_label">' . __( 'Homepage', 'text_domain' ) . '</label></th>';
		echo '		<td>';
		echo '			<input type="url" id="certificate_url" name="certificate_url" class="certificate_url_field" placeholder="' . esc_attr__( '', 'text_domain' ) . '" value="' . esc_attr( $certificate_url ) . '">';
		echo '			<p class="description">' . __( 'Homepage der Auszeichnung oder der Zertifikats', 'text_domain' ) . '</p>';
		echo '		</td>';
		echo '	</tr>';

		echo '	<tr>';
		echo '		<th><label for="certificate_runtime" class="certificate_runtime_label">' . __( 'Laufzeit', 'text_domain' ) . '</label></th>';
		echo '		<td>';
		echo '			<input type="date" id="certificate_runtime" name="certificate_runtime" class="certificate_runtime_field" placeholder="' . esc_attr__( '', 'text_domain' ) . '" value="' . esc_attr( $certificate_runtime ) . '">';
		echo '			<p class="description">' . __( 'Laufzeit des Zertifikats', 'text_domain' ) . '</p>';
		echo '		</td>';
		echo '	</tr>';

		echo '</table>';

	}

	public function save_metabox( $post_id, $post ) {

		// Check if the user has permissions to save data.
		if ( ! current_user_can( 'edit_post', $post_id ) )
			return;

		// Sanitize user input.
		$certificate_new_url = isset( $_POST[ 'certificate_url' ] ) ? esc_url( $_POST[ 'certificate_url' ] ) : '';
		$certificate_new_runtime = isset( $_POST[ 'certificate_runtime' ] ) ? sanitize_text_field( $_POST[ 'certificate_runtime' ] ) : '';

		// Update the meta field in the database.
		update_post_meta( $post_id, 'certificate_url', $certificate_new_url );
		update_post_meta( $post_id, 'certificate_runtime', $certificate_new_runtime );

	}

}

new mb_certificate;