Hi @FlaminSeraphim,
OJS 2.4.x will currently not work with PHP7. (See this issue for details.)The 7.0 release introduced a String class, and OJS already includes its own, so the two collide. We’ll rename the String class in a future release, but for the moment PHP7 has very low adoption so it hasn’t been a high priority.
If you’ve moved to PHP 5.6 and don’t get the installation form, it’s likely a file permissions problem in your cache subdirectory. Review the installation instructions and ensure those are correct.
Regards,
Alec Smecher
Public Knowledge Project Team