the_post_thumbnail 在 WordPress 中主要用来打印文章中设定的缩略图，而 get_the_post_thumbnail 函数可以将你需要的 HTML 代码以字符串的形式返回。
the_post_thumbnail 函数的使用
the_post_thumbnail($size,$attr)
函数参数$size 是指你想要的缩略图类型 默认是 ‘post-thumbnail’ 也就是特色图像
$attr 图像img标签中的属性设置。
the_post_thumbnail 函数声明
/** * Display Post Thumbnail. * * @since 2.9.0 * * @param int $size Optional. Image size. Defaults to 'post-thumbnail', which theme sets using set_post_thumbnail_size( $width, $height, $crop_flag );. * @param string|array $attr Optional. Query string or array of attributes. */functionthe_post_thumbnail($size='post-thumbnail',$attr=''){echoget_the_post_thumbnail(null,$size,$attr);}
get_the_post_thumbnail 函数声明
*Retrieve Post Thumbnail.**@since 2.9.0 **@param int $post_idOptional.Post ID.*@param string $sizeOptional.Image size.Defaults to 'post-thumbnail'.*@param string|array$attrOptional.Query string or arrayof attributes.*/functionget_the_post_thumbnail($post_id=null,$size='post-thumbnail',$attr=''){$post_id=(null===$post_id)? get_the_ID():$post_id;$post_thumbnail_id=get_post_thumbnail_id($post_id);$size=apply_filters('post_thumbnail_size',$size);if($post_thumbnail_id){do_action('begin_fetch_post_thumbnail_html',$post_id,$post_thumbnail_id,$size);// for "Just In Time" filtering of all of wp_get_attachment_image()'s filtersif(in_the_loop())update_post_thumbnail_cache();$html=wp_get_attachment_image($post_thumbnail_id,$size,false,$attr);do_action('end_fetch_post_thumbnail_html',$post_id,$post_thumbnail_id,$size);}else{$html='';}returnapply_filters('post_thumbnail_html',$html,$post_id,$post_thumbnail_id,$size,$attr);}