PHP: require_once

Last updated: Fri, 05 Sep 2008

require_once()

require_once()文は、スクリプトの実行中に指定されたファイルを読み込み、評価します。この振る舞いはrequire() 文と似ていて、唯一の違いは既にコードが読み込まれている場合には再度読み込まれることがないことです。この文がどのように動作するかについては require()を参照してください。

require_once()は、スクリプトの実行時に同じファイルが複数回読み込まれ、評価される可能性がある場合に、関数の再定義や変数値の再代入といった問題を回避するために一回だけ読み込ませるために使用します。

require_once()および include_once()の使用例に関する他の例については、最新のPHPソースコード配布ファイルに含まれる » PEARのコードを参照ください。

戻り値は、include()と同じです。ファイルが既にインクルードされている場合、この関数は TRUEを返します。

注意: require_once()はPHP 4.0.1で追加されました。

注意: (Windowsのように)大文字小文字を区別しないオペレーティングシステムでは、 require_once()および include_once()の動作が意図したものにならない可能性があるので注意してください。

例1 require_once() はWindowsでは大文字小文字を区別しません

require_once "a.php"; // a.phpを読み込みます require_once "A.php"; // Windowsはこれもa.phpを読み込みます! (PHP 4のみ)

この動作は、PHP 5で変更されました。パスはまず正規化されます。このため、 C:\PROGRA~1\A.phpは C:\Program Files\a.phpと同じと認識され、ファイルは一回だけ読み込まれます。

警告

PHP 4.3.0 より前のバージョンの Windows 版 PHP は、現在この関数に関してリモートファイルアクセス機能をサポートしていません。これは、allow_url_fopen を有効にした場合でも同様です。

require(), include(), include_once(), get_required_files(), get_included_files(), readfile(), virtual()も参照してください。

include_once

include

Last updated: Fri, 05 Sep 2008

add a note User Contributed Notes
require_once

cnorthcote at underground dot co dot uk
14-Mar-2008 11:20


Bear in mind that require_once doesn't have a return value (neither does require; since they both halt execution on failure), so this won't work:



<?



require_once("path/to/myfile.php") or die("Couldn't load myfile");



?>



because you will get a very unhelpful error:



PHP Fatal error:  require_once() : Failed opening required '1' (include_path='.;C:\\php5\\pear') in C:\path\to\code.php on line 1



This was mentioned on the php-general mailing list in about 2003 but is a gotcha I have seen a few people come across. If you want to check to see if a file was included, use @include() instead.

amcewen at look dot ca
11-Feb-2008 03:00


Perhaps it would be clearer to say that require_once() includes AND evaluates the resulting code once.  More specifically, if there is code in the script file other than function declarations, this code will only be executed once via require_once().

Sinured
20-Aug-2007 06:33


Beware: As miqrogroove said below, require_once() is not independent of require() -- but vice versa, require() IS independent of require_once()!

Let's turn miqrogroove's example around:



echo.php

<?php

echo "42!<br />\n";

?>



test.php

<?php

require_once 'echo.php';

require 'echo.php';

// 42!

// 42!

?>



So: require_once() will NOT include a file previously included by require(), while require WILL include a file previously included by require_once.

manuel schaffner
14-Jun-2007 10:02


The path for nested require_once() is always evaluated relative to the called / first file containing require_once(). To make it more flexible, maintain the include_path (php.ini) or use set_include_path() - then the file will be looked up in all these locations.

jazfresh at hotmail.com
08-Mar-2007 07:22


Check how many files you are including with get_required_files(). If it's a significant number (> 100), it may be worth "compiling" the main PHP file. By "compiling", I mean write a script that reads a PHP file and replaces any "include/require_once" references with either:

- the file that it's requiring

- a blank line if that file has been included before



This function can be recursive, thus building up a large PHP file with no require_once references at all. The speedup can be dramatic. On one of our pages that included 115 classes, the page was sped up by 60%.

sneskid at hotmail dot com
19-Jan-2007 08:00


<?php

function & rel($r, &$f) {return file_exists( ( $f = ( dirname($r).'/'.$f ) ) );}

function & relf($r, $f) {return rel($r,$f) ? file_get_contents($f) : null;}

function & reli($r, $f) {return rel($r,$f) ? include($f) : null;}

function & relr($r, $f) {return rel($r,$f) ? require($f) : null;}

function & relio($r, $f) {return rel($r,$f) ? include_once($f) : null;}

function & relro($r, $f) {return rel($r,$f) ? require_once($f) : null;}

?>



I found it useful to have a function that can load a file relative to the calling script and return null if the file did not exist, without raising errors.



<?php

/*

Load file contents or return blank if it's not there.

Relative to the file calling the function.

*/

echo relf(__FILE__, 'some.file');

?>



It was easy to modify and just as useful for require/include.



<?php

/*

Require the file once.

It's like suppressing error messages with @ but only when the file does not exist.

Still shows compile errors/warning, unless you use @relro().

Relative to the file calling the function.

*/

relro(__FILE__, 'stats.php');

?>



If you work with a deep php file structure and a barrage of includes/requires/file-loads this works well.

rejjn at mail dot nu
01-Sep-2006 10:28


The following only applies to case insensitive systems like Windows.



Even though the documentation sais that "the path is normalized" that doesn't seem to be true in all cases. 



If you are using the magic __autoload() function (or if the framework you're using is using it) and it includes the requested class file with complete path or if you override the include path in mid execution, you may have some very strange behavior. The most subtle problem is that the *_once functions seem to differentiate between c:\.... and C:\....



So to avoid any strange problems and painfull debugging make sure ALL paths you use within the system have the same case everywhere, and that they correspond with the actual case of the filesystem. That includes include paths set in webserver config/php.ini, auto load config, runtime include path settings or anywhere else.

antoine dot pouch at mcgill dot ca
10-Mar-2006 03:13


require_once (and include_once for that matters) is slow. 

Furthermore, if you plan on using unit tests and mock objects (i.e. including mock classes before the real ones are included in the class you want to test), it will not work as require() loads a file and not a class.



To bypass that, and gain speed, I use :



<?php

class_exists('myClass') || require('path/to/myClass.class.php');

?>



I tried to time 100 require_once on the same file and it took the script 0.0026 seconds to run, whereas with my method it took only 0.00054 seconds. 4 times faster ! OK, my method of testing is quite empirical and YMMV but the bonus is the ability to use mock objects in your unit tests.

martijn(dot)lowrider(at)gmail(dot)com
24-Feb-2006 07:00


How to use Require_Once with error reporting to include a MySQL Connection file:



-------------------------------------------------------------------

$MySQLConnectFile = './inc/MySQL.Class.php';



if ( is_dir ( './inc/' ) )

{

    $IncIsDir == TRUE;

}



if ( file_exists ( $MySQLConnectFile ) )

{

    $MySQLFileExists == TRUE;

}



if ( $IncIsDir && $MySQLFileExists )

{

    require_once ( $MySQLConnectFile )

}

else

{

    echo '<b>Error:</b> <i>Could not read the MySQL Connection File. Please try again later.';

    exit();

}



----------------------------------------------------------------------

sdh00b at gmail dot com
05-Dec-2005 03:12


@georg_gruber at yahoo dot com



Files for including are first looked in include_path relative to the current working directory and then in include_path relative to the directory of current script. E.g. if your include_path is ., current working directory is /www/, you included include/a.php and there is include "b.php" in that file, b.php is first looked in /www/ and then in /www/include/. If filename begins with ./ or ../, it is looked only in include_path relative to the current working directory.



Taken from http://us2.php.net/manual/en/function.include.php

georg_gruber at yahoo dot com
06-Oct-2005 11:06


A very interesting behaviour of require_once (and probably all include commands):



consider the following files:



/index.php -> require_once('/inc/library.php');

/function1.php -> print('/function1.php');

/inc/library.php -> require_once('function1.php');

/inc/function1.php -> print('/inc/function1.php');



Note that /function1.php and /inc/function1.php are files with the SAME filename in different folders.



If you "/index.php" is executed it will output

"/function1.php".



Although /index.php "includes" /inc/library.php the scope of the file is still /index.php therefor /function1.php will be found even it could be asumed the /inc/function1.php is the correct one.



And it gets more interesting: if you delete /function1.php and execute /index.php PHP checks this and "includes" /inc/function1.php.

miqrogroove
01-May-2005 07:10


require_once() is NOT independent of require().  Therefore, the following code will work as expected:



echo.php

<?php

echo "Hello";

?>



test.php

<?php

require('echo.php');

require_once('echo.php');

?>



test.php outputs: "Hello".



Enjoy,

-- Miqro

ulderico at maber dot com dot br
22-Mar-2005 01:38


With both of your functions guys, Pure-PHP and jtaal at eljakim dot nl, you'll not have any variables available GLOBALly if they're supposed to be globals...



That's why my import handles better those situation. OK, SOME MAY DISPUTE that using include_once and require_once may slow down an application. But what's the use to do IN PHP what the interpreter *should* do better for you. Thusly these workarounds shall, some time in the future, DIE.



Thus It's better to well design your application to keep some order using few INCLUDES and REQUIRES in it rather than insert MANY AND SEVERAL *_once around.

Pure-PHP
17-Mar-2005 10:19


require_once can slower your app, if you include to many files.



You cann use this wrapper class, it is faster than include_once 



http://www.pure-php.de/node/19



require_once("includeWrapper.class.php")



includeWrapper::require_once("Class1.class.php");

includeWrapper::require_once("Class1.class.php");

includeWrapper::require_once("Class2.class.php")

jtaal at eljakim dot nl
10-Mar-2005 01:00


When you feel the need for a require_once_wildcard function, here's the solution:



<?php // /var/www/app/system/include.inc.php



function require_once_wildcard($wildcard, $__FILE__) {

  preg_match("/^(.+)\/[^\/]+$/", $__FILE__, $matches);

  $ls = `ls $matches[1]/$wildcard`;

  $ls = explode("\n", $ls);

  array_pop($ls); // remove empty line ls always prints

  foreach ($ls as $inc) {

    require_once($inc);

  }

}



?>



The $__FILE__ variable should be filled with the special PHP construct __FILE__:

<?php // /var/www/app/classes.inc.php



require_once('system/include.inc.php');

require_once_wildcard("classes/*.inc.php", __FILE__);



?>



The (*.inc.php) files inside the directory classes are automagically included using require_once_wildcard.



This solution may not be as useful when using PHP5 in combination with classes and the autoload feature.



--

Jaap Taal

thomas dot revell at uwe dot ac dot uk
21-Jan-2005 10:00


Regarding the case insensitivity problems on Windows, it looks to me as though it is a problem in PHP5 as well (at least in some cases).



The following gave me problems:



From file URLSwitcher.php

<?php

require_once 'slimError/slimError.php';

require_once 'Navigator_Cache.php';

....

?>



From file Navigator_Cache.php

<?php

require_once 'slimError/slimerror.php';

...

?>



From file slimerror.php

<?php

class SLIMError {

...

}

?>

The above setup gave me an error : "Cannot redeclare class SLIMError"



If I change the require_once in URLSwitcher.php to match the one in Navigator_Cache.php, there isn't a problem, but if I do this the other way round, the same problem occurs.

18-Mar-2004 05:49


> Mac OS X systems are also not case-sensitive.

That depends on the filesystem:

- HFS and HFS+ are NOT case sensitive.

- UFS is case sensitive.

add a note

include_once

include

Last updated: Fri, 05 Sep 2008