Hi, I upgraded php to 5.6.32 and now my older flynax websites are broken.

It shows:
Fatal error: Incompatible file format: The encoded file has format major ID 4, whereas the Loader expects 7 in /home/xxxxxxxxx/public_html/includes/classes/rlNavigator.class.php on line 0


Please advise on how to fix this and not have it be a problem everytime there is a php upgrade.

Thanks.