WordPress at a glance
filter is not described

post_class filter-hook . WP 2.7.0

Filters the list of CSS classes for the current post.

Usage

add_filter( 'post_class', 'filter_function_name_1176', 10, 3 );
function filter_function_name_1176( $classes, $class, $post_id ){
	// filter...

	return $classes;
}
$classes(array)
An array of post classes.
$class(array)
An array of additional classes added to the post.
$post_id(int)
The post ID.

Where the hook is called

get_post_class()
post_class
wc_get_product_class()
wp-includes/post-template.php 547
$classes = apply_filters( 'post_class', $classes, $class, $post->ID );
woocommerce/includes/wc-template-functions.php 637
return array_filter( array_unique( apply_filters( 'post_class', $classes, $class, $post->ID ) ) );

Where the hook is used (in WP core)

Does not used.