The code of 'LxHelper::objecttocommalist' mean WHMCS call their 'objecttocommalist' function via 'static' calling and this context 'objecttocommalist' must declare with 'static function objecttocommalist('. Possible WHMCS declare 'objecttocommalist' not as static function. And it's make warning 'Strict Standards: Non-static method LxHelper::objectToCommaList() should not be called statically'.
This issue also discuss for Kloxo official.
Example:
1. Calling statically:
$a = LxHelper::objecttocommalist();
2. Calling dynamically (with assumption LxHelper as object:
$t = new LxHelper();
$a = $t->cttocommalist();