Relative path or absolute path and how to set up in PHP

I have a site that I am working on and I am trying to go to the main directory of the site and I do not know how to set that up. What I am trying to do is include _inc/config.php through /_inc/config.php instead of having to use ../_inc/config.php Any ideas how to add this?

Generally speaking, there are two different problems to solve when dealing with paths:

Filesystem paths (which you need to use to include a file)
URL paths (which you need to use when building a URL internal to your application)

These are two different beasts.

Filesystem paths

If your application has a single point of entry (e.g. an index.php which then delegates to the appropriate business logic after inspecting the URL query string), then you can do

$ROOT_DIR = dirname(__FILE__);

inside that file, and then you can compose filesystem paths for any file in your distribution by appending to $ROOT_DIR.

If your application does not have a single point of entry, then this option is not available and you are left with these alternatives:

Use relative paths everywhere (this is what you would like to avoid).
Call a "path-resolution" function from your current entry script, passing the relative path of the script to the base directory as a parameter, for example:

// for a script in $ROOT_DIR.'/commands' do this:

$ROOT_DIR = resolve_root(__FILE__, DIRECTORY_SEPARATOR.'commands');

The additional relative path information will enable resolve_root($filename, $relative) to figure out which part of dirname($filename) is the application root. However, the technique is unwieldy and requires that you hardcode relative path names inside every application entry point, so I would recommend against ever using it.
Require that your application's configuration includes a hardcoded variable with the "root" path, similar to $ROOT_DIR above. If your application has an installer, then during installation you can have it resolve the root path accurately by doing something like:

$installer_dir = dirname(__FILE__); // assume this is root path + "/install" $ROOT_DIR = realpath($installer_dir.DIRECTORY_SEPARATOR.'..');

The installer would then write this path to your application configuration. If your application has no installer, then you need to either hardcode the base path to your configuration manually or use another option.

Using $_SERVER['DOCUMENT_ROOT'] is not a satisfactory solution to this problem. It does the job only if your application is installed at the document root. If your document root is /var/www and your application is installed in /var/www/app, then you have no way of knowing that you should add /app to the paths.

Update: Regarding the answer that mentions running pwd on Linux: please don't do that. Ever. Invoking the system shell for each HTTP request is going to kill your web server faster than your users can click on your links. It could work for an internal application that has a known small number of users and no real expectations of performance, but why not simply hardcode that path if your are fine with a quick and dirty solution?

URL paths

Inside any real application you will also need to create URLs relative to the base URL of your application (for example, to do <img src="$BASE_URL/images/icon.png" />).

Again, if your application has a single entry point (e.g. index.php) then you can use $_SERVER['REQUEST_URI'] to resolve the "base" URL of your application. A simple implementation (that should work fine for you) is simple: it's the part of the URL path that comes before index.php. However, a bulletproof implementation that works around the quirks of different web servers and PHP configurations is somewhat more complicated.

If your application does not have a single entry point, then you have the same problem as with filesystem paths. The solution is also the same: either hardcode the URL in your configuration manually, have an installer hardcode it during installation, or resolve it using hardcoded knowledge of your relative paths as required.

includes work via either filesystem or http.

if you use include /some/file.php PHP looks in the server root.

You can use

include $_SERVER['DOCUMENT_ROOT'] . '/some/file.php';

or perhaps change open_basedir in php.ini (or.htaccess). i.e. open_basedir=/some/where/ to use /file.php from THAT root directory instead of the server's root or document root. Also check the "paths and directories" section in php.ini

I use absolute paths, but I also start any custom PHP project with a bootstrap file where I define the most commonly used paths as constants, based on values extracted from $_SERVER.

This is how I define my root paths :

define("LOCAL_PATH_ROOT", $_SERVER["DOCUMENT_ROOT"]);
define("HTTP_PATH_ROOT", isset($_SERVER["HTTP_HOST"]) ? $_SERVER["HTTP_HOST"] : (isset($_SERVER["SERVER_NAME"]) ? $_SERVER["SERVER_NAME"] : '_UNKNOWN_'));

The path LOCAL_PATH_ROOT is the document root. The path HTTP_PATH_ROOT is the equivalent when accessing the same path via HTTP.

At that point, converting any local path to an HTTP path can be done with the following code :

str_replace(LOCAL_PATH_ROOT, RELATIVE_PATH_ROOT, $my_path)

If you want to ensure compatibility with Windows based servers, you'll need to replace the directory seperator with a URL seperator as well :

str_replace(LOCAL_PATH_ROOT, RELATIVE_PATH_ROOT, str_replace(DIRECTORY_SEPARATOR, '/', $my_path))

Here's the full bootstrap code that I'm using for the PHP PowerTools boilerplate :

defined('LOCAL_PATH_BOOTSTRAP') || define("LOCAL_PATH_BOOTSTRAP", __DIR__);

// -----------------------------------------------------------------------
// DEFINE SEPERATOR ALIASES
// -----------------------------------------------------------------------
define("URL_SEPARATOR", '/');
define("DS", DIRECTORY_SEPARATOR);
define("PS", PATH_SEPARATOR);
define("US", URL_SEPARATOR);

// -----------------------------------------------------------------------
// DEFINE ROOT PATHS
// -----------------------------------------------------------------------
define("RELATIVE_PATH_ROOT", '');
define("LOCAL_PATH_ROOT", $_SERVER["DOCUMENT_ROOT"]);
define("HTTP_PATH_ROOT",
        isset($_SERVER["HTTP_HOST"]) ?
        $_SERVER["HTTP_HOST"] : (
        isset($_SERVER["SERVER_NAME"]) ?
        $_SERVER["SERVER_NAME"] : '_UNKNOWN_'));

// -----------------------------------------------------------------------
// DEFINE RELATIVE PATHS
// -----------------------------------------------------------------------
define("RELATIVE_PATH_BASE",
        str_replace(LOCAL_PATH_ROOT, RELATIVE_PATH_ROOT, getcwd()));
define("RELATIVE_PATH_APP", dirname(RELATIVE_PATH_BASE));
define("RELATIVE_PATH_LIBRARY", RELATIVE_PATH_APP . DS . 'vendor');
define("RELATIVE_PATH_HELPERS", RELATIVE_PATH_BASE);
define("RELATIVE_PATH_TEMPLATE", RELATIVE_PATH_BASE . DS . 'templates');
define("RELATIVE_PATH_CONFIG", RELATIVE_PATH_BASE . DS . 'config');
define("RELATIVE_PATH_PAGES", RELATIVE_PATH_BASE . DS . 'pages');
define("RELATIVE_PATH_ASSET", RELATIVE_PATH_BASE . DS . 'assets');
define("RELATIVE_PATH_ASSET_IMG", RELATIVE_PATH_ASSET . DS . 'img');
define("RELATIVE_PATH_ASSET_CSS", RELATIVE_PATH_ASSET . DS . 'css');
define("RELATIVE_PATH_ASSET_JS", RELATIVE_PATH_ASSET . DS . 'js');

// -----------------------------------------------------------------------
// DEFINE LOCAL PATHS
// -----------------------------------------------------------------------
define("LOCAL_PATH_BASE", LOCAL_PATH_ROOT . RELATIVE_PATH_BASE);
define("LOCAL_PATH_APP", LOCAL_PATH_ROOT . RELATIVE_PATH_APP);
define("LOCAL_PATH_LIBRARY", LOCAL_PATH_ROOT . RELATIVE_PATH_LIBRARY);
define("LOCAL_PATH_HELPERS", LOCAL_PATH_ROOT . RELATIVE_PATH_HELPERS);
define("LOCAL_PATH_TEMPLATE", LOCAL_PATH_ROOT . RELATIVE_PATH_TEMPLATE);
define("LOCAL_PATH_CONFIG", LOCAL_PATH_ROOT . RELATIVE_PATH_CONFIG);
define("LOCAL_PATH_PAGES", LOCAL_PATH_ROOT . RELATIVE_PATH_PAGES);
define("LOCAL_PATH_ASSET", LOCAL_PATH_ROOT . RELATIVE_PATH_ASSET);
define("LOCAL_PATH_ASSET_IMG", LOCAL_PATH_ROOT . RELATIVE_PATH_ASSET_IMG);
define("LOCAL_PATH_ASSET_CSS", LOCAL_PATH_ROOT . RELATIVE_PATH_ASSET_CSS);
define("LOCAL_PATH_ASSET_JS", LOCAL_PATH_ROOT . RELATIVE_PATH_ASSET_JS);

// -----------------------------------------------------------------------
// DEFINE URL PATHS
// -----------------------------------------------------------------------
if (US === DS) { // needed for compatibility with windows
    define("HTTP_PATH_BASE", HTTP_PATH_ROOT . RELATIVE_PATH_BASE);
    define("HTTP_PATH_APP", HTTP_PATH_ROOT . RELATIVE_PATH_APP);
    define("HTTP_PATH_LIBRARY", false);
    define("HTTP_PATH_HELPERS", false);
    define("HTTP_PATH_TEMPLATE", false);
    define("HTTP_PATH_CONFIG", false);
    define("HTTP_PATH_PAGES", false);
    define("HTTP_PATH_ASSET", HTTP_PATH_ROOT . RELATIVE_PATH_ASSET);
    define("HTTP_PATH_ASSET_IMG", HTTP_PATH_ROOT . RELATIVE_PATH_ASSET_IMG);
    define("HTTP_PATH_ASSET_CSS", HTTP_PATH_ROOT . RELATIVE_PATH_ASSET_CSS);
    define("HTTP_PATH_ASSET_JS", HTTP_PATH_ROOT . RELATIVE_PATH_ASSET_JS);
} else {
    define("HTTP_PATH_BASE", HTTP_PATH_ROOT .
            str_replace(DS, US, RELATIVE_PATH_BASE));
    define("HTTP_PATH_APP", HTTP_PATH_ROOT .
            str_replace(DS, US, RELATIVE_PATH_APP));
    define("HTTP_PATH_LIBRARY", false);
    define("HTTP_PATH_HELPERS", false);
    define("HTTP_PATH_TEMPLATE", false);
    define("HTTP_PATH_CONFIG", false);
    define("HTTP_PATH_PAGES", false);
    define("HTTP_PATH_ASSET", HTTP_PATH_ROOT .
            str_replace(DS, US, RELATIVE_PATH_ASSET));
    define("HTTP_PATH_ASSET_IMG", HTTP_PATH_ROOT .
            str_replace(DS, US, RELATIVE_PATH_ASSET_IMG));
    define("HTTP_PATH_ASSET_CSS", HTTP_PATH_ROOT .
            str_replace(DS, US, RELATIVE_PATH_ASSET_CSS));
    define("HTTP_PATH_ASSET_JS", HTTP_PATH_ROOT .
            str_replace(DS, US, RELATIVE_PATH_ASSET_JS));
}

// -----------------------------------------------------------------------
// DEFINE REQUEST PARAMETERS
// -----------------------------------------------------------------------
define("REQUEST_QUERY",
        isset($_SERVER["QUERY_STRING"]) && $_SERVER["QUERY_STRING"] != '' ?
        $_SERVER["QUERY_STRING"] : false);
define("REQUEST_METHOD",
        isset($_SERVER["REQUEST_METHOD"]) ?
        strtoupper($_SERVER["REQUEST_METHOD"]) : false);
define("REQUEST_STATUS",
        isset($_SERVER["REDIRECT_STATUS"]) ?
        $_SERVER["REDIRECT_STATUS"] : false);
define("REQUEST_PROTOCOL",
        isset($_SERVER["HTTP_ORIGIN"]) ?
        substr($_SERVER["HTTP_ORIGIN"], 0,
        strpos($_SERVER["HTTP_ORIGIN"], '://') + 3) : 'http://');
define("REQUEST_PATH",
        isset($_SERVER["REQUEST_URI"]) ?
        str_replace(RELATIVE_PATH_BASE, '',
        $_SERVER["REQUEST_URI"]) : '_UNKNOWN_');
define("REQUEST_PATH_STRIP_QUERY",
        REQUEST_QUERY ?
        str_replace('?' . REQUEST_QUERY, '', REQUEST_PATH) : REQUEST_PATH);

// -----------------------------------------------------------------------
// DEFINE SITE PARAMETERS
// -----------------------------------------------------------------------
define("PRODUCTION", false);
define("PAGE_PATH_DEFAULT", US . 'index');
define("PAGE_PATH",
        (REQUEST_PATH_STRIP_QUERY === US) ?
        PAGE_PATH_DEFAULT : REQUEST_PATH_STRIP_QUERY);

If you add the above code to your own project, outputting all user constants at this point (which can do with get_defined_constants(true) should give a result that looks somewhat like this :

array (
  'LOCAL_PATH_BOOTSTRAP' => '/var/www/libraries/backend/Data/examples',
  'URL_SEPARATOR' => '/',
  'DS' => '/',
  'PS' => ':',
  'US' => '/',
  'RELATIVE_PATH_ROOT' => '',
  'LOCAL_PATH_ROOT' => '/var/www',
  'HTTP_PATH_ROOT' => 'localhost:8888',
  'RELATIVE_PATH_BASE' => '/libraries/backend/Data/examples',
  'RELATIVE_PATH_APP' => '/libraries/backend/Data',
  'RELATIVE_PATH_LIBRARY' => '/libraries/backend/Data/vendor',
  'RELATIVE_PATH_HELPERS' => '/libraries/backend/Data/examples',
  'RELATIVE_PATH_TEMPLATE' => '/libraries/backend/Data/examples/templates',
  'RELATIVE_PATH_CONFIG' => '/libraries/backend/Data/examples/config',
  'RELATIVE_PATH_PAGES' => '/libraries/backend/Data/examples/pages',
  'RELATIVE_PATH_ASSET' => '/libraries/backend/Data/examples/assets',
  'RELATIVE_PATH_ASSET_IMG' => '/libraries/backend/Data/examples/assets/img',
  'RELATIVE_PATH_ASSET_CSS' => '/libraries/backend/Data/examples/assets/css',
  'RELATIVE_PATH_ASSET_JS' => '/libraries/backend/Data/examples/assets/js',
  'LOCAL_PATH_BASE' => '/var/www/libraries/backend/Data/examples',
  'LOCAL_PATH_APP' => '/var/www/libraries/backend/Data',
  'LOCAL_PATH_LIBRARY' => '/var/www/libraries/backend/Data/vendor',
  'LOCAL_PATH_HELPERS' => '/var/www/libraries/backend/Data/examples',
  'LOCAL_PATH_TEMPLATE' => '/var/www/libraries/backend/Data/examples/templates',
  'LOCAL_PATH_CONFIG' => '/var/www/libraries/backend/Data/examples/config',
  'LOCAL_PATH_PAGES' => '/var/www/libraries/backend/Data/examples/pages',
  'LOCAL_PATH_ASSET' => '/var/www/libraries/backend/Data/examples/assets',
  'LOCAL_PATH_ASSET_IMG' => '/var/www/libraries/backend/Data/examples/assets/img',
  'LOCAL_PATH_ASSET_CSS' => '/var/www/libraries/backend/Data/examples/assets/css',
  'LOCAL_PATH_ASSET_JS' => '/var/www/libraries/backend/Data/examples/assets/js',
  'HTTP_PATH_BASE' => 'localhost:8888/libraries/backend/Data/examples',
  'HTTP_PATH_APP' => 'localhost:8888/libraries/backend/Data',
  'HTTP_PATH_LIBRARY' => false,
  'HTTP_PATH_HELPERS' => false,
  'HTTP_PATH_TEMPLATE' => false,
  'HTTP_PATH_CONFIG' => false,
  'HTTP_PATH_PAGES' => false,
  'HTTP_PATH_ASSET' => 'localhost:8888/libraries/backend/Data/examples/assets',
  'HTTP_PATH_ASSET_IMG' => 'localhost:8888/libraries/backend/Data/examples/assets/img',
  'HTTP_PATH_ASSET_CSS' => 'localhost:8888/libraries/backend/Data/examples/assets/css',
  'HTTP_PATH_ASSET_JS' => 'localhost:8888/libraries/backend/Data/examples/assets/js',
  'REQUEST_QUERY' => false,
  'REQUEST_METHOD' => 'GET',
  'REQUEST_STATUS' => false,
  'REQUEST_PROTOCOL' => 'http://',
  'REQUEST_PATH' => '/',
  'REQUEST_PATH_STRIP_QUERY' => '/',
  'PRODUCTION' => false,
  'PAGE_PATH_DEFAULT' => '/index',
  'PAGE_PATH' => '/index',
)

来源：https://stackoverflow.com/questions/4650517/relative-path-or-absolute-path-and-how-to-set-up-in-php

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