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action is not described

begin_fetch_post_thumbnail_html action-hook . WP 2.9.0

Fires before fetching the post thumbnail HTML.

Provides "just in time" filtering of all filters in wp_get_attachment_image().

Usage

add_action( 'begin_fetch_post_thumbnail_html', 'action_function_name_306', 10, 3 );
function action_function_name_306( $post_id, $post_thumbnail_id, $size ){
	// action...
}
$post_id(int)
The post ID.
$post_thumbnail_id(string)
The post thumbnail ID.
$size(string/array)
The post thumbnail size. Image size or array of width and height values (in that order).
Default: 'post-thumbnail'

Where the hook is called

get_the_post_thumbnail()
wp-includes/post-thumbnail-template.php 151
do_action( 'begin_fetch_post_thumbnail_html', $post->ID, $post_thumbnail_id, $size );

Where the hook is used (in WP core)

wp-includes/default-filters.php 371
add_action( 'begin_fetch_post_thumbnail_html', '_wp_post_thumbnail_class_filter_add' );