the_post_thumbnail issues

the_post_thumbnail() prints the HTML immediately. Use get_the_post_thumbnail() instead to get the HTML into your string.

$content .= '<div class="thumbnail">' 
    . get_the_post_thumbnail( null, "home-post-thumbnail") 
    . '</div>';

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)