WordPress hacked[.PHP Headers Modified]

My WordPress installation along with the other php files inside the server was compromised by a malware attack just few days ago. The source is not known but restored a backup still the code is there, its a common issue, on the top of each .php file a malware code has been inserted.

I’d like to know if there is any way to disinfect this automatically, rather to remove the header file or something like that in each of the files. I checked the backups and all have been infected it seems.

Any help?