identifier    = $identifier;
		$this->heading_level = $heading_level;
		$this->title         = $title;
		$this->content       = $content;
		$this->url           = $url;
	}
	/**
	 * Returns the premium popup as an HTML string.
	 *
	 * @param bool $popup Show this message as a popup show it straight away.
	 *
	 * @return string
	 */
	public function get_premium_message( $popup = true ) {
		// Don't show in Premium.
		if ( defined( 'WPSEO_PREMIUM_FILE' ) ) {
			return '';
		}
		$assets_uri = trailingslashit( plugin_dir_url( WPSEO_FILE ) );
		/* translators: %s expands to Yoast SEO Premium */
		$cta_text        = esc_html( sprintf( __( 'Get %s', 'wordpress-seo' ), 'Yoast SEO Premium' ) );
		$new_tab_message = '' . esc_html__( '(Opens in a new browser tab)', 'wordpress-seo' ) . '';
		$caret_icon      = '';
		$classes         = '';
		if ( $popup ) {
			$classes = ' hidden';
		}
		$micro_copy = __( '1 year free support and updates included!', 'wordpress-seo' );
		$popup = <<