Wordpress - fix child CSS version cache

gistfile1.txt

function _fix_child_css_version( $src ) {
	$parts = explode( '?', $src );
	if ( stristr( $parts[0], '-child/style.css' ) ) {
		$child_ver = filemtime( get_stylesheet_directory() . '/style.css' );
		return $parts[0] . '?v=' . $child_ver;
	}
	else {
		return $src;
	}
}
add_filter( 'style_loader_src', '_fix_child_css_version', 15, 1 );