[kh99]

Originally Posted by MyLibary

May i ask what the last row mean?
vB_Template:reRegister('header', array('custom_header_mysite_beta' => $customheader));

Before you can use something like {vb:raw custom_header_mysite_beta} in a template, you must register (or preRegister) a value for custom_header_mysite_beta. There's an article describing this process here: https://vborg.vbsupport.ru/showthread.php?t=228078 (Sorry, I probably should have sent you to that article first).

What is that $customheader and what if i change it to something else?

You can change it to whatever you want as long as you change it on the line above as well. The point is that the result of render() is what is registered to custom_header_mysite_beta. ($customheader is just a temporary variable).