Blank page for PHP pages when 1st load after restart

Hi!

I am trying to visualize php pages using my own c++ program (with
Webbrowser class)

Apache seems to work well. Except for some PHP files which are
displayed as a blank page when the first time I access it after
restart the computer. If I reload it, the page is well displayed. I
don't have any error messages in my logs.

Any Ideas?

Thanks in advance!