Use of PHP functions for debugging thumbnails in WordPress

This article describes how to use PHP functions to debug thumbnails in WordPress, including using set_post_thumbnail_size to adjust the thumbnail size. For more information, see The_post_thumbnail
The_post_thumbnail is mainly used to print the thumbnail set in the article in WordPress, while the get_the_post_thumbnail function can return the HTML code you need as a string.

Use of the_post_thumbnail function

the_post_thumbnail( $size , $attr)

Function parameters

• $ Size indicates the type of the thumbnail you want. the default value is 'post-thumbnail ', which is also a special image.
• $ Attr attributes in the image img label.

The_post_thumbnail function declaration

/*** 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. */function the_post_thumbnail ($ size = 'post-thumbnail ', $ attr = '') {echo get_the_post_thumbnail (null, $ size, $ attr);} get _ The_post_thumbnail function declaration * Retrieve Post Thumbnail. ** @ since 2.9.0 ** @ param int $ post_id Optional. post ID. * @ param string $ size Optional. image size. ULTS to 'post-thumbnail '. * @ param string | array $ attr Optional. query string or array of attributes. */function get_the_post_thumbnail ($ post_id = null, $ size = 'post-thumbnail ', $ attr = '') {$ post_id = (null = $ post_id )? Get_the_ID (): $ post_id; $ post_thumbnail_id = response ($ post_id); $ size = apply_filters ('post _ thumbnail_size ', $ size); if ($ post_thumbnail_id) {do_action ('In In _ fetch_post_thumbnail_html ', $ post_id, $ post_thumbnail_id, $ size); // for "Just In Time" filtering of all of wp_get_attachment_image ()'s filters if (in_the_loop () evaluate (); $ html = wp_get_attachment_image ($ post_thumbnail_id, $ size, false, $ attr); do_action ('end _ upload ', $ post_id, $ post_thumbnail_id, $ size);} else {$ html = '';} return apply_filters ('post _ thumbnail_html ', $ html, $ post_id, $ post_thumbnail_id, $ size, $ attr );

Set_post_thumbnail_size
The set_post_thumbnail_size function is a function used to set the special image size in WordPress. it is also a simple application of the add_image_size function. To better highlight the use of special images, WordPress has been available since version 2.9.0.

Set_post_thumbnail_size function usage
This function is similar to the add_image_size function, except that it only sets the special image.

set_post_thumbnail_size( $width, $height, $crop)

Parameter details

• $ Width: Image width
• $ Height image height
• $ Crop: whether to crop the image based on the height and width

Instance

set_post_thumbnail_size(100,0,true);

Note: when either the height or width is 0, WP automatically adapts to the other value for generating thumbnails.

Function declaration

/** * Registers an image size for the post thumbnail * * @since 2.9.0 */function set_post_thumbnail_size( $width = 0, $height = 0, $crop = false ) { add_image_size( 'post-thumbnail', $width, $height, $crop );