Intallation Error: PHP is not running

After having followed every step of the wp installation and the server setup, when I click ok install.php file I got the following Error: PHP is not running.

I’ve checked and checked againg with my server and everything seems to be fine and moreover I already create a website using a web4web server and wordpress, but this time I got this problem and I can’t solve it.

Thank for the help.
Marco