Internal Server Error

Array to string conversion

[lib/f3/base.php:2174] Base->error()
[lib/f3/base.php:974] Base->{closure}()
[lib/f3/base.php:366] Base->language()
[lib/f3/f3.php:39] Base->set()
[lib/pages/basic.php:101] pages\basic->set_lan()
[lib/pages/basic.php:19] pages\basic->get_lan()
[lib/f3/base.php:1737] ReflectionClass->newInstanceArgs()
[lib/f3/base.php:1758] Base->grab()
[lib/f3/base.php:1609] Base->call()
[lib/f3/f3.php:39] Base->run()