My website is returning a 'No input file specified' error rather than a 404 error page when an invalid php page is accessed. Why is this happening and can I fix it?

When running PHP as a CGI Binary and not in library mode, Apache will send any PHP based request directly to the php executable without verifying if the request is valid. This can cause seemingly random errors such as the 'No input file specified' message. The good news is that this is easily resolved by using an .htaccess directive.

Here is the code that you will want to use to resolve this issue,

RewriteEngine On
RewriteCond %{DOCUMENT_ROOT}%{REQUEST_URI} !-f
RewriteRule ^.+\.php$ /junkfile
 

This code will work so long as you do not have a file called 'junkfile' in your default content tree.