require()

The require() statement includes and evaluates the specific file.

require() includes and evaluates a specific file. Detailed information on how this inclusion works is described in the documentation for include().

require() and include() are identical in every way except how they handle failure. include() produces a Warning while require() results in a Fatal Error. In other words, don't hesitate to use require() if you want a missing file to halt processing of the page. include() does not behave this way, the script will continue regardless. Be sure to have an appropriate include_path setting as well.

Пример 16-4. Basic require() examples

<?php require 'prepend.php'; require $somefile; require ('somefile.txt'); ?>

See the include() documentation for more examples.

Замечание: Prior to PHP 4.0.2, the following applies: require() will always attempt to read the target file, even if the line it's on never executes. The conditional statement won't affect require(). However, if the line on which the require() occurs is not executed, neither will any of the code in the target file be executed. Similarly, looping structures do not affect the behaviour of require(). Although the code contained in the target file is still subject to the loop, the require() itself happens only once.

Замечание: Поскольку это языковая конструкция, а не функция, она не может вызываться при помощи переменных функций

Внимание

Версии PHP для Windows до PHP 4.3.0 не поддерживают возможность использования удаленных файлов этой функцией даже в том случае, если опция allow_url_fopen включена.

require

gabe at websaviour dot com
13-Jul-2006 05:42


If you are experiencing a bug related to using relative paths with include or require, it may be related to a grandparent directory that is executable but not readable.  It will cause __FILE__ to return a relative path instead of the full path which it is supposed to show.  This manifests itself in interesting ways that can be seemingly unrelated.  For instance, I discovered it using the Smarty {debug} command which failed to find its template due to this issue.  Please see the following for more details:



http://bugs.php.net/bug.php?id=34552

http://shiftmanager.net/~kurt/test/

Inc
31-May-2006 08:35


I have found a problem when I try to access a php file via require($class_directory)



// # $class_directory contain a long full path and dot into the last folder.

// # $class_directory = "/var/.../app/system/plugintoto_1.0/class_plugintoto_1.0.php";



// dot ('.') and minus ('-') are not accepted in require !

tjeerd
11-May-2006 06:41


When using symbolic links with PHP, specify a dotslash './page.php' path to ensure that PHP is looking in the right directory with nested requires:



E.g. when the required actual page1.php contains other require statements to, say page2.php, PHP will search the path that the symbolic link points to, instead of the path where the symbolic link lives. To let PHP find the other page2.php in the path of the symbolic link, a require('./page2.php'); statement will solve the puzzle.

webmaster at netgeekz dot net
24-Feb-2006 09:34


I have learnt to manipulate this code into an effecitve and easy to use form. I use it with require_once, but it could be used for require.



require_once($_SERVER['DOCUMENT_ROOT'].'/includes/top.php');



This mainly jumps back to the servers document root and then begins to enter the directories defined until it finds the file. In this case it would go back to the root of the server, or whatever your document root is, and then enter includes. there it would search for the top.php file. Simple to use, yet effective...espcially for people like me who re-use code or move files to different directories. I don't have to fix the includes, because they all work the same way.

steve at walkerfx dot com
24-Feb-2006 03:24


WARNING: Be absolutely sure that your include paths are relative or directory based and not http!!!



   require("http://www.mydomain.com/somefile.php"); //WRONG!!

   require("usr/mydomain/somefile.php"); //CORRECT!!



If you are intending to access local files and you accidentally use an http address, the request will probably work. However, this creates a wierd situation that can cause all sorts of bugs in your scripts and slow your code down.



The problem is that the include spawns off another php request, and is essentially requesting the file in the same a way a remote viewer would. So rather than including the intended php code, instead you get the processed output from that single file executed in its own private scope.



It's a simple mistake, but it can be an awful problem to debug.



Walker

dave at davidhbrown dot us
22-Jan-2006 12:08


re: danielm at unb dot br...



$_SERVER['DOCUMENT_ROOT'] is very useful, but it is not available with all web servers. Apache has it; IIS doesn't. 



I use the following to make my PHP applications work in more situations:

<?php

if (!defined("BASE_PATH")) define('BASE_PATH', isset($_SERVER['DOCUMENT_ROOT']) ? $_SERVER['DOCUMENT_ROOT'] : substr($_SERVER['PATH_TRANSLATED'],0, -1*strlen($_SERVER['SCRIPT_NAME'])));

?>



...but even that gets tripped up by symlinks to different mount points, etc. You could substitute realpath($_SERVER['PATH_TRANSLATED']), but that function has been reported not to work on some (Windows) servers. One could use the PATH_TRANSLATED for both servers, but I figure if Apache is going to tell me exactly what I want to know, I should listen.

tuxedobob at mac dot com
06-Jul-2005 11:54


Something which may not be immediately obvious is that if you use double quotes on the filename, you can use variables to specify the filename, allowing you to do something like this:



<?php

$query = "SELECT filename FROM updates WHERE version>$current ORDER BY version";

$updateresult = mysql_query($query) or exit($query.'<br />'.mysql_error());

while ($updaterow = mysql_fetch_row($updateresult)) {

    require "$updaterow[0]";

}

?>



Drop this in a script on a server and you can push updates to your clients. Obviously, make sure you only run scripts you want to.

Marc
06-May-2005 10:42


This will sound elementary, but for C++ native programmers, be sure NOT to put a '#' in front of your include statements! The parser will not give you an error, but also will not include the file, making for a tedious debugging process.



In short, USE:

<?php

     include "yourfile.php";

?>



and DON'T use:

<?php

     #include "yourfile.php";

?>

richardbrenner(-at- )gmx(-)at
07-Apr-2005 01:58


If you use relativ paths in a php script (file A) that can be required by another php script (file B), be aware that the relativ paths in file A will be relativ to the directory, where file B is stored. 

You can use the following syntax in file A, to be sure that the paths are relativ to the directory of file A:



<?

require(dirname(__FILE__)."/path/relative/file_to_include.php");

?>



Greetings,

Richard

10-Feb-2005 10:29


Note when calling any require or include function, that the call will block if the script given as the parameter is excecuting.

Because of this one should be careful when using blocking functions like sleep() in a script which is included by another.

danielm at unb dot br
21-Nov-2004 11:50


if you want to include files with an absolut path reference, you can use:



require ($_SERVER["DOCUMENT_ROOT"]."/path/to/file.php");



this way you can organize your files in subdirectories trees.