DOCTYPE Override in effect! php error

[xAdrianRonsten]

Hello, I'm currently trying to validate my php code as xhtml strict 1.0 and keep getting this error.
How do i solve it? would be really happy if someone could help me out. Thanks!

 

[Mucski]

<!DOCTYPE html> is enough.

 

[s-p-n]

that error isn't caused by PHP. You should properly learn DOCTYPEs and the specifications for writing your own web-sites.