2
If I were you, I would:
1. Go into your database.
2. Browse the table xoops_config.
3. Modify the record for debug_mode.
4. Change the value that is in the conf_value field to 1.
5. Troubleshoot any errors that appear while trying to do the actions that you explained above.
**The actions above, should turn on PHP Debug mode.
Good Luck!