PLEASE check disable_functions of phpinfo()/php.ini,Prestashop need scandir support.
Many php.ini disable scandir.
1
Please go to PrestaShopAutoload.php row 184, it need scandir function.
Because it need create cache/class_index.php content.
When you got the Fatal Error or HTTP ERROR 500, you can see the cache/class_index.php, but no content is in it.
It shoule have file path, type and override.
2
Folder config and cache should chmod -R 777 before you install