woocommerce_placeholder_img_src │ filter-hook │ WC 1.0

Usage

add_filter( 'woocommerce_placeholder_img_src', 'wp_kama_woocommerce_placeholder_img_src_filter' );

/**
 * Function for `woocommerce_placeholder_img_src` filter-hook.
 * 
 * @param  $src 
 *
 * @return 
 */
function wp_kama_woocommerce_placeholder_img_src_filter( $src ){

	// filter...
	return $src;
}

$src

-

Where the hook is called

return apply_filters( 'woocommerce_placeholder_img_src', $src );

Where the hook is used in WooCommerce