Adds an extra metabox on WordPress pages to allow a page to have a tagline

tagline_meta_box.php

<?php
function debthelpline_add_meta_boxes(){

	// Add the Subheading meta box
	add_meta_box( 'debthelpline_banner_subheading', __( 'Banner Subheading', 'debthelpline' ), 'debthelpline_subheading_meta_box', 'page', 'normal', 'high' );

}
add_action( 'add_meta_boxes', 'debthelpline_add_meta_boxes' );
function debthelpline_subheading_meta_box( $post ) {

	// Use nonce for verification
	wp_nonce_field( plugin_basename( __FILE__ ), 'debthelpline_meta_box_nonce' );

	$banner_subheading = get_post_meta( $post->ID, 'debthelpline_banner_subheading', true );

	if( $banner_subheading === false )
		$banner_subheading = '';

	// The actual fields for data entry ?>
	<p>The banner subheading appears below the site title on the page's banner image.</p>
	<label for="debthelpline_banner_subheading"><?php _e( 'Banner subheading:', 'debthelpline' ); ?></label>
	<input type="text" id="debthelpline_banner_subheading" name="debthelpline_banner_subheading" value="<?php echo $banner_subheading; ?>" size="25" />
<?php
}

/**
 * When the post is saved, saves our custom data
 */
function debthelpline_save_meta_box_data( $post_id ) {

	if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) 
		return;

	if ( ! wp_verify_nonce( $_POST['debthelpline_meta_box_nonce'], plugin_basename( __FILE__ ) ) )
		return;

	if( isset( $_POST['debthelpline_banner_subheading'] ) ) {

		update_post_meta( $post_id, 'debthelpline_banner_subheading', $_POST['debthelpline_banner_subheading'] );

	}
}
add_action( 'save_post', 'debthelpline_save_meta_box_data' );
?>