What exactly is PATH_INFO in PHP?

Question

all external URLs look like 'module/action?key1=param1'. No customization possible--but it's fast. The difference is that the first uses PHP's GET, and the second uses PATH_INFO.

I've seen PATH_INFO several times, but still don't know what exactly it is. What does it do?

Answer 1

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

Answer 2

As the variable PATH_INFO is part of the definition for CGI you should also take a look in there ;)

The PATH_INFO variable specifies a path to be interpreted by the CGI script. It identifies the resource or sub-resource to be returned by the CGI script, and is derived from the portion of the URI path hierarchy following the part that identifies the script itself. Unlike a URI path, the PATH_INFO is not URL-encoded, and cannot contain path-segment parameters. A PATH_INFO of "/" represents a single void path segment.

 PATH_INFO = "" | ( "/" path )  path      = lsegment *( "/" lsegment )  lsegment  = *lchar  lchar     = <any TEXT or CTL except "/"> 

https://www.rfc-editor.org/rfc/rfc3875#section-4.1.5