1. PHP REQUIREMENT LINK : https://justblab.com/blabax-php-ajax-website-chat-software
2. In Blab 20.08 we have kept minimum PHP requirement as PHP 5.4.0, as script throws error on PHP 5.3. Check if it works on PHP 5.3 in next version. 
(Doesn't work on PHP 5.3 , checked in Blab 20.09 as well)