What Exactly Is Path_Info in PHP

What exactly is PATH_INFO in PHP?

Actually, PATH_INFO is related to the Apache Web Server serving PHP pages and not PHP per se.

PATH_INFO is an environment variable set by Apache when the AcceptPathInfo directive is turned on. It will contain trailing pathname information that follows an actual filename or non-existent file in an existing directory, whether the request is accepted or rejected. Environment variables are then passed on to the Apache/CGI module in charge of rendering the page.

The variable is accessible in PHP using $_SERVER['PATH_INFO'].

For example, assume the location /test/ points to a directory that contains only the single file here.html. Then requests for /test/here.html/more and /test/nothere.html/more both collect /more as PATH_INFO.

Apache Core Documentation: AcceptPathInfo Directive

What is the difference between $_SERVER['PATH_INFO'] and $_SERVER['ORIG_PATH_INFO']?

The PATH_INFO variable is only present if you invoke a PHP script like this:

http://www.example.com/phpinfo.php/HELLO_THERE

It's only the /HELLO_THERE part after the .php script. If you don't invoke the URL like that, there won't be a $_SERVER["PATH_INFO"] environment variable.

The PORIG_ prefix is somewhat uncommon. PATH_INFO is a standard CGI-environment variable, and should never be prefixed. Where did you read that? (There were some issues around PHP3/PHP4 if you invoked the PHP interpreter via cgi-bin/ - but hardly anyone has such setups today.)

For reference: http://www.ietf.org/rfc/rfc3875

Check in PHP if PATH_INFO is enabled on your server?

I don't think there is a defined way to get hold of an Apache configuration value like that.

One idea that comes to mind is making a request using file_get_contents() to

http://current_site_domain/check.php/test

check.php would output $_SERVER['PATH_INFO'].

If the result of the request is "test", PATH_INFO works.

Of course, this might fail because opening URLs is disabled, because you don't know the local domain, because there's a firewall in place, etc. etc.

Another way that is less prone to failing is using an iframe:

<iframe src="/check.php/It%20works!"></iframe>

If you see "it works" inside the ifrane, PATH_INFO works. Possibly useful for an installation procedure.

PATH_INFO in PHP without having file apparent

When a webpage is requested from a server. The server looks at the path (i.e. example.com/this/is/a/path) to figure out which file to serve and from where.

As I understand it, what you want to do is have your index.php handle all the requests. The way you would do this to use URL Rewriting.

Assuming you are using an apache web server, you can use something called *mod_rewrite* to do this. See more on mod_rewrite here.

For the specific rules to use, you probably want to use something like the code in V_K's answer.

Portable and safe way to get PATH_INFO

Well, I'm (almost) sure that without making use of the $_SERVER superglobal keys, providing a alternative way to figure out PATH_INFO is just impossible, that being said lets first list all of the $_SERVER keys that we may possibly use:

'PHP_SELF'
'QUERY_STRING'
'SCRIPT_FILENAME'
'PATH_TRANSLATED'
'SCRIPT_NAME'
'REQUEST_URI'
'PATH_INFO'
'ORIG_PATH_INFO'

We obviously need to ignore the last two. Now we should (I don't know this for a fact, I'm just assuming because you said so) filter all the keys that exist in the link you provided (which BTW is offline ATM), that leaves us with the following keys:

'PHP_SELF'
'SCRIPT_FILENAME'
'REQUEST_URI'

Regarding your comment to Anthonys answer:

You are just juggling variables now.
SCRIPT_FILENAME is a part of the CGI
spec. It will not be available if
PATH_INFO is unavailable. As for
REQUEST_URI, it's apache's mod_rewrite
specific. – LiraNuna

I'm running LightTPD/1.4.20-1 (Win32) with PHP 5.3.0 as CGI, cgi.fix_pathinfo = 1 and $_SERVER['REQUEST_URI'] is very available to me, I also remember using that same variable back in the days when no one used mod_rewrite so my honest humble guess is that you're plain wrong in this point. Regarding the SCRIPT_FILENAME key I'm unable to test that one out ATM. Still, if we close our eyes really hard and believe that you're right that leaves us with only one variable:

'PHP_SELF'

I'm not trying in being harsh here (and I still believe that there are more solutions) but if PHP_SELF is the only key you want us to work with (assuming there are no impositions on PHP_SELF itself) there is only one solution left:

function PATH_INFO()
{
 if (array_key_exists('PATH_INFO', $_SERVER) === true)
 {
  return $_SERVER['PATH_INFO'];
 }

 $whatToUse = basename(__FILE__); // see below

 return substr($_SERVER['PHP_SELF'], strpos($_SERVER['PHP_SELF'], $whatToUse) + strlen($whatToUse));
}

This function should work, however there may be some problems using the __FILE__ constant since it returns the path to the file where the __FILE__ constant is declared and not the path to the requested PHP script, so that's why the $whatToUse is there for: sou you can replace it with 'SCRIPT_FILENAME' or if you really believe in what you are saying, just use '.php'.

You should also read this regarding why not to use PHP_SELF.

If this doesn't work for you, I'm sorry but I can think of anything else.

EDIT - Some more reading for you:

Drupal request_uri() (why do they keep saying REQUEST_URI is Apache specific?)
PHP_SELF vs PATH_INFO vs SCRIPT_NAME vs REQUEST_URI

PHP_SELF vs PATH_INFO vs SCRIPT_NAME vs REQUEST_URI

The PHP documentation can tell you the difference:

'PHP_SELF'

The filename of the currently executing script, relative to the document root. For instance, $_SERVER['PHP_SELF'] in a script at the address http://example.com/test.php/foo.bar would be /test.php/foo.bar. The __FILE__ constant contains the full path and filename of the current (i.e. included) file. If PHP is running as a command-line processor this variable contains the script name since PHP 4.3.0. Previously it was not available.

'SCRIPT_NAME'

Contains the current script's path. This is useful for pages which need to point to themselves. The __FILE__ constant contains the full path and filename of the current (i.e. included) file.

'REQUEST_URI'

The URI which was given in order to access this page; for instance, '/index.html'.

PATH_INFO doesn't seem to be documented...

$_SERVER['PATH_INFO'] on localhost

If your url looks like this
http://localhost/ then $_SERVER['PATH_INFO'] is not set.

What Exactly Is Path_Info in PHP