I upgraded to php7.0 this weekend, now I can not save any articels in K2 anymore. Error message is
Call to undefined function ereg()

When I turn of SEOBOSS message disappears, but I get a 504 Gateway Time-Out when saving...
What to do?

Thanks in advance

Hello,

The PHP error is related to SEOBOSS (since turning it off resolves the issue).

As for the 504 error, this means that the server did not recieve a timely response. To resolve this you can,

a) Report it to your hosting provider,
b) Disable 3rd party extensions to see which one is causing this.