A while back, I wrote about dealing with the Apache / FastCGI error ‘Primary script unknown’ when trying to access non-existent PHP files. Bots often do this trying to test for vulnerabilities, and it can fill up error logs and be annoying to look through. In that post, I fixed the problem through mod_rewrite and a RewriteCond. For PHP 2.4+, there is a more broad and likely more efficient solution using the <If> directive. It will work for all virtual hosts on a server.
When setting up Apache as a web server and adding PHP support, there will generally be a SetHandler directive somewhere in the Apache configuration (usually somewhere in /etc/apache2 or /etc/httpd) that sends requests for PHP files to a special handler. On Ubuntu, this would be in /etc/apache2/conf-enabled/php8.1-fpm.conf if using PHP FPM, or /etc/apache2/mods-enabled/php8.1.conf if using mod_php. Adding the <If> would look something like this:
<IfModule !mod_php8.c>
<IfModule proxy_fcgi_module>
<FilesMatch ".+\.ph(ar|p|ps|tml)$">
<If "-f %{REQUEST_FILENAME}">
SetHandler "proxy:unix:/run/php/php8.1-fpm.sock|fcgi://localhost"
</If>
</FilesMatch>
</IfModule>
</IfModule>
for PHP FPM. For mod_php:
<FilesMatch ".+\.ph(ar|p|tml)$">
<If "-f %{REQUEST_FILENAME}">
SetHandler application/x-httpd-php
</If>
</FilesMatch>
These will simply not set the special PHP handler for the request if the file doesn’t exist. If you have a RewriteRule common for CMS’s like:
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
requests for matching URLs will still go through index.php as normal, as the rewrite will change the request to a file that does exist.
No more worthless ‘Primary script unknown’ errors to need to parse through when looking at logs.