Is it possible to access REQUEST_FILENAME through PHP?

Question

I am trying to understand the following htaccess rule in more detail:

<IfModule mod_rewrite.c> RewriteEngine On RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteCond %{REQUEST_URI} !^/(favicon\.ico|apple-touch-icon.*\.png)$ [NC] RewriteRule (.+) index.php?p=$1 [QSA,L] </IfModule> 

In particular, I am trying to understand how REQUEST_FILENAME works. There are several resources that I found discussing this from the mod_rewrite docs to answer this question in Stack Overflow. But no one seems to be addressing exactly what I'm looking for, and how can I look at the REQUEST_FILENAME variable in more detail to see its value?

Typically, when I want to look at a variable referenced in .htaccess, I will use print_r to look at the global value of $ _SERVER to find out what server values ​​are:

 echo "<pre>"; print_r($_SERVER); echo "</pre>"; die('fin'); 

This may help me see values ​​like $ _SERVER ['REQUEST_URI'] above. But it does not seem that REQUEST_FILENAME is available in any of the PHP $ GLOBALS in my current environment. I see the value for SCRIPT_FILENAME, and several sources say that the two values ​​are equal, but it is not clear whether they are substitute or REQUEST_FILENAME returns to SCRIPT_FILENAME if the first is not present.

I managed to output the REQUEST_FILENAME value by slightly modifying the htaccess rule to output the value to the URL, changing the last line to:

 RewriteRule (.+) index.php?p=%{REQUEST_FILENAME} [R=302,QSA,L] 

But why is this value not available anywhere in PHP? Is there something I am missing that can help me figure out where this variable is stored and how to view its value through PHP?

Answer 1

From RewriteCond

REQUEST_FILENAME
The full path of the local file system to the file or script corresponding to the request, if it was already determined by the server at the time of the REQUEST_FILENAME link. Otherwise, for example, when used in the context of a virtual host, the same value as REQUEST_URI. Depending on the value of AcceptPathInfo, the server can use only some of the leading REQUEST_URI components to match the request with the file.

and $_SERVER

'SCRIPT_FILENAME'
The absolute name of the current executable script.

It will be the same (full path to the script) if REQUEST_URI actually matches the existing file.

If it is not, REQUEST_FILENAME will simply be REQUEST_URI , and SCRIPT_FILENAME will be the name of the executable file of the PHP script. $_SERVER['REQUEST_URI'] will be REQUEST_FILENAME (aka REQUEST_URI ).

In your case, SCRIPT_FILENAME will always be /path/to/index.php , and REQUEST_FILENAME / REQUEST_URI will be available through $_SERVER['REQUEST_URI'] .

Update

REQUEST_URI will never be a file name because it lacks the root prefix of the document. When you use

 RewriteCond %{REQUEST_URI} !-f 

the condition will always be true, even if the requested URL matches an existing file. The next RewriteRule will always be executed, although it should call another PHP script or serve HTML, CSS or an image file.

Update

To answer the question.

But why is this value not available in PHP?

REQUEST_FILENAME not available in PHP because it is not in the environment or in the request headers.

All you can see in PHP is either an environment variable, or in the headers, or something that PHP can do. Since PHP does not try or cannot establish a connection between the request URI and some file name, you cannot access it anywhere. REQUEST_FILENAME can be anywhere on the file system.

You can, however, put it in the environment yourself

 RewriteRule (.+) index.php?p=$1 [QSA,L,E=REQUEST_FILENAME:%{REQUEST_FILENAME}] 

and access it in PHP as $_SERVER['REDIRECT_REQUEST_FILENAME'] .