Wordpress Shortcode with multiple Variables

shortcode.php

<?php

function ppai_quotebox( $atts ) {
  
	$templateDirectory = get_bloginfo('template_directory');
	
	extract( shortcode_atts( array(
			'imgpath' => $templateDirectory.'/images/quote-dummy.jpg',
			'quote' => 'Ohne ein Zitat sehe ich scheisse aus',
			'author' => 'Die Zitatbox',
  ), $atts ) );

  $render_quotebox = 
		'<section class="project-quote group">'.
			'<figure><img src="'.$imgpath.'" alt="'.$author.'" /></figure>'.
			'<div class="project-quote-quote">'.
				'<blockquote>»'.$quote.'«</blockquote>'.
				'<p>'.$author.'</p>'.
			'</div>'.
		'</section>';
	
	return $render_quotebox;
}
add_shortcode( 'quotebox', 'ppai_quotebox' );