Create category post shortcode

Needs a complete rewrite…

add_shortcode( 'categorypost', 'cat_post' );

function cat_post( $atts ) {

    // attributes for shortcode
   if ( isset( $atts['cat'] ) ) {$cats = $atts['cat'];} else {return;}
   if ( isset( $atts['posts_per_page'] ) ) {$posts_per_page = $atts['posts_per_page'];} else {$posts_per_page = -1;}

   // get the category posts
   $category = get_category_by_slug( $cats );
   if ( !is_object( $category ) ) {return;}
   $args = array(
        'cat' => $category->term_id,
        'posts_per_page' => $posts_per_page
   );
   $posts = get_posts( $args );

   // create the list output
   if ( count( $posts ) > 0 ) {
       foreach ( $posts as $post ) {
           $link = get_permalink( $post->ID );
           $title = $post->post_title;
           $image = get_post_thumbnail( $post->ID,'thumbnail' );
           $output .= '<div id="postrow-'.$post->ID.'" class="postrow">';
           $output .= '<a class="postlink" href="'.$link.'">' . $image;
           $output .= '<h5 class="posttitle">' . $title . '</h5></a></div>';
       }
   }
   return $output;
}

Example shortcode usage: [categorypost cat="pant" posts_per_page="5"]