In case you encounter this error upon installing b2evo you can check the solution below.
Error: Fatal error: Allowed memory size of 8388608 bytes exhausted (tried to allocate 35 bytes) in /var/www/…/_misc/_plugins.class.php on line 2399
Solution: In most cases you have your php.ini inside the installed folder of b2evo, increase the allowed memory size and it will fix the error.