/**
* wpse135208_cat_thumb_from_random_child.
*
* Get the thumbnail from a random post belonging to one of the child categories.
*
* @version 0.1
*
* @link https://wordpress.stackexchange.com/q/135208/22534
*
* @param integer $c_cat (default: '')
* @param string/array $size (default: 'post-thumbnail')
* @param string/array $attr (default: null)
*
* @return string
*/
function wpse135208_cat_thumb_from_random_child( $c_cat = '', $size = 'post-thumbnail', $attr = null ) {
// do nothing if $c_cat is empty
if( empty($c_cat) ) return;
// get_terms is used because we only need ids
$taxonomies = array(
'category'
);
$args = array(
'child_of' => $c_cat,
'fields' => 'ids'
);
// returns an array of ids
$child_cats = get_terms( $taxonomies, $args );
// use this for debugging
//echo '<pre>'; print_r($child_cats); echo '</pre>';
$args = array(
// we use numberposts instead of post_per_page,
// because if the pre_get_posts filter is used,
// it can make a difference in this case
// we only want one post
'numberposts' => 1,
// but we randomize this
'orderby' => 'rand',
'category__in' => $child_cats,
'fields' => 'ids',
// make sure only posts with featured image are considered
'meta_query' => array(
array(
'key' => '_thumbnail_id',
'compare' => 'EXISTS'
)
)
);
// returns an array containing one post id
$ct_p_id = get_posts( $args );
// use this for debugging
//echo '<pre>'; print_r($ct_p_id); echo '</pre>';
// use this for debugging
//echo '<pre>'; print_r( ( 1 /*change to 0 to show src info*/ ) ? get_the_post_thumbnail( $ct_p_id[0], $size, $attr ) : wp_get_attachment_image_src( get_post_thumbnail_id( $ct_p_id[0] ) ) ); echo '</pre>';
// now we can use this to return our thumbnail
return get_the_post_thumbnail( $ct_p_id[0], $size, $attr );
}
/**
* wpse135208_cat_thumb_wrapper.
*
* Wrapper function to have the ability to use predefined image sizes via wp_get_attachment_image().
*
* @version 0.1
*
* @link https://wordpress.stackexchange.com/q/135208/22534
*
* @param integer $category_id (default: null)
* @param string/array $size (default: 'thumbnail')
* @param boolean $icon (default: false)
* @param string/array (default: null)
*
* @return string
*/
function wpse135208_cat_thumb_wrapper( $category_id = null, $size = 'thumbnail', $icon = false, $attr = null ) {
$category_thumbnail_obj = get_the_category_data( $category_id );
return wp_get_attachment_image( $category_thumbnail_obj->id, $size, $icon, $attr );
}
