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require

(PHP 4, PHP 5)

require() 语句包含并运行指定文件。有关包括如何工作的详细信息见 include() 的文档。

require() 和 include() 几乎完全一样，除了处理失败的方式不同之外。include() 产生一个Warning而 require() 则导致一个 Fatal Error。换句话说，如果想在丢失文件时停止处理页面，那就别犹豫了，用 require() 吧。include() 就不是这样，脚本会继续运行。同时也要确认设置了合适的include_path。

Example #1 基本的 require() 例子

<?php

require 'prepend.php';

require $somefile;

require ('somefile.txt');

?>

更多例子参见 include() 文档。

Note:

在 PHP 4.0.2 之前适用以下规则：require() 总是会尝试读取目标文件，即使它所在的行根本就不会执行。条件语句不会影响 require()。不过如果 require() 所在的行没有执行，则目标文件中的代码也不会执行。同样，循环结构也不影响 require() 的行为。尽管目标文件中包含的代码仍然是循环的主体，但 require() 本身只会运行一次。

查看 include 文档了解如何工作的。

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PHP手册 - N: require

用户评论:

bsntech (01-Mar-2011 09:41)

If you use the require directive to load a file, your script will die if the file is not found or the user that is running the web server does not have read access to it.  In some cases, this is ok - but if you want a site to still function for visitors without displaying a white page, use the 'include' directive instead.

When using 'include', the site will still load - minus any materials that is in that file.

Brian S.

carlo_greco at live dot it (27-Jun-2010 12:04)

If you want to get a parsed PHP file, e.g file.php contains echo 'ciao'; the function below will return you the output of file.php that is ciao

<?php
// file and get, if you need to include a file.php?query_string.

function pinclude($file, $type, $get = null) {
    $p = explode('/', $file);
    $file = end($p);
    $dir = '';
    $n = count($p) - 1;

    for($i = 0; $i < $n; $i++)
        $dir .= $p[$i] . '/';

    if($get !== null) {
        $tmp = $_GET; // back up
        $_GET = array();
        $get = explode('&', $get);
        $n = count($get);

        for($i = 0; $i < $n; $i++) {
            if(strpos($get[$i], '=') === false)
                $_GET[$get[$i]] = 1;
            else {
                list($name, $val) = explode('=', $get[$i], 2);
                $_GET[$name] = $val;
            }
        }
    }

    ob_start();
    chdir($dir);
    require $file;
    $out = ob_get_clean();

    if($tmp)
        $_GET = $tmp;

    return $out;
}

$out = pinclude('./dir/yourfile.php', 'a=b&c=d&e');
echo $out;
// i'm sorry but i forgot post requests...
?>

Wing (10-May-2010 01:04)

if you want always include, require, open files using some 'root' folder based path you may may put file '.htroot' in 'root' folder and  use this.

while(!file_exists(getcwd()."/.htroot")){chdir('..');}

This code change current dir to dir where '.htroot' file located and everywhere you can use relative to 'root' paths.

Please avoid absent of '.htroot' file.

pedro dot evangelista at gmail dot com (16-Dec-2008 02:23)

Be careful when using symbolic links, because require will search the real path of the file and not the path relative to the symbolic link.

Imagine your script A.php resides on directory /a and you create a symbolic link for it on directory /b/c.
So for the code

<?php
echo realpath("../");
?>

you might expect the directory /b, but actually you get the root directory /.

If you need to include the file /b/B.php inside your A.php, you can't use the following

<?php
require "../B.php";
?>

because it will search the root directory, not the /b directory.

Regards.

duccio at getlocal dot it (23-Nov-2008 09:37)

In response to some dot user at notarealdomain dot com:

This is because require executes the code "as if" it was code written inside of the function, inheriting everything including the scope. But here there is something even more interesting:

<requiredfile.php>:
<?php

$this->a.=" is visible also under a require\n";
$b="While the variable b is a local variable of the function\n";
function FunctionUnderRequire() {
    echo "But the functions declared inside of a require called from a class function, just as when defined from inside any other function, are always global\n";
}
?>

<mainfile.php>:
<?php

error_reporting(E_ALL|E_STRICT);

class UserClass {

    protected $a;

    public function UserFunction() {
        $this->a='The class variable a';
        require 'requiredfile.php';
        echo $this->a; // "The class variable a  is visible also under a require\n"
        echo $this->b; // Notice: Undefined property: UserClass::$b
        echo $b; // "While the variable b is a local variable of the function\n"
        $this->FunctionUnderRequire(); //Fatal error!
        FunctionUnderRequire(); // "But the functions..."
    }
}

$UserClass=new UserClass;
$UserClass->UserFunction();
?>

I'm wondering if there is a method for declaring class public/private/protected functions from inside a require/include...

ricardo dot ferro at gmail dot com (14-May-2008 07:15)

Two functions to help:

<?php

function add_include_path ($path)
{
    foreach (func_get_args() AS $path)
    {
        if (!file_exists($path) OR (file_exists($path) && filetype($path) !== 'dir'))
        {
            trigger_error("Include path '{$path}' not exists", E_USER_WARNING);
            continue;
        }
       
        $paths = explode(PATH_SEPARATOR, get_include_path());
       
        if (array_search($path, $paths) === false)
            array_push($paths, $path);
       
        set_include_path(implode(PATH_SEPARATOR, $paths));
    }
}

function remove_include_path ($path)
{
    foreach (func_get_args() AS $path)
    {
        $paths = explode(PATH_SEPARATOR, get_include_path());
       
        if (($k = array_search($path, $paths)) !== false)
            unset($paths[$k]);
        else
            continue;
       
        if (!count($paths))
        {
            trigger_error("Include path '{$path}' can not be removed because it is the only", E_USER_NOTICE);
            continue;
        }
       
        set_include_path(implode(PATH_SEPARATOR, $paths));
    }
}

?>

Peter McDonald (16-Oct-2007 05:21)

re the comment by moazzamk at gmail dot com

As the manual states require and require_once as of PHP 4.02 no longer call the file if the line of code it is on should not be executed.

scott (20-Sep-2007 09:27)

If you want to verify that a file can be included or required, the simplest solution I've found is just to check that the file exists.

<?php

    if(file_exists($pageContentInc)){
        require_once $pageContentInc;
    }else{
        $pageContentInc = "common/content_404.inc";
        require_once $pageContentInc;
    }
?>

Does it really need to be any harder than that?

daniel at nohair dot com (07-Sep-2007 03:24)

I love php.  But when file can't be included, 'require' or 'require_once' throw fatal error and halt the script, which is almost never desirable on a mission-critical production server.  I think it may be better to use something like the following. 

<?php

if (@include 'plan_A.php') {
    // Plan A;
} elseif (@include 'plan_B.php') {
    // Plan B;
} else {
    // Hope never happens.  If does, then Email the webmaster;
    // Call 911, Medic, Fire, Police, the president;
    // Change hard drive, server, hosting service;
}

?>

Or handle trouble first is you wish

<?php

if (!@include 'plan_A.php') {
    // Someone has kidnapped/corrupted Plan_A.php;
    // Email the webmaster;
    // Change hard drive, server, hosting service;
} else {
    // Plan A;
}

?>

moazzamk at gmail dot com (17-Jul-2007 04:51)

require and include read the included files even if they are not executed in the code. You can use eval() to avoid this.

eval('require filename;');

I don't know if it's faster to have the files included the regular way or the eval way though (in other words, I haven't tested their efficiency). It will be great if someone can test which is better.

some dot user at notarealdomain dot com (11-Jul-2007 03:58)

Discovered a bit of weird behavior yesterday involving require() (using PHP 5.2.3).  If you use require() inside a function, the "globals" in the file will be local to the function.  An example of this:

test.php:
<?php
  function TestFunc()
  {
    require('test2.php');
    echo "<pre>" . print_r($GLOBALS, true) . "</pre>";
  }
?>

test2.php:
<?php
  $MyTestGlobal = Array();
?>

This happens because require is a statement that _inlines_ the target code - not a function that gets called.

To fix this, use the $GLOBALS superglobal:

test2.php:
<?php
  $GLOBALS["MyTestGlobal"] = Array();
?>

chris at chrisstockton dot org (20-Jun-2007 01:06)

Remember, when using require that it is a statement, not a function. It's not necessary to write:
<?php
 require('somefile.php');
?>

The following:
<?php
require 'somefile.php';
?>

Is preferred, it will prevent your peers from giving you a hard time and a trivial conversation about what require really is.

(31-Jan-2007 11:38)

A note that drove me nuts for 2 days!

Be carfull if you have a newline or blank space befor your php tags in the included/required file it will read as html and outputed.

If your running your output through javascript string evaluations which would be sensitive to newlines/white spaces be carfull that the first chars in the file are the php tages eg <?php

bmessenger at 3servicesolution dot com (17-Oct-2006 09:06)

// Looks like I might have a fix for some on the
// relative path issue.

if (!function_exists('bugFixRequirePath'))
{
    function bugFixRequirePath($newPath)
    {
        $stringPath = dirname(__FILE__);
        if (strstr($stringPath,":")) $stringExplode = "\\";
        else $stringExplode = "/";
       
        $paths = explode($stringExplode,$stringPath);
       
        $newPaths = explode("/",$newPath);
       
        if (count($newPaths) > 0)
        {
            for($i=0;$i<count($newPaths);$i++)
            {
                if ($newPaths[$i] == "..") array_pop($paths);   
            }
           
            for($i=0;$i<count($newPaths);$i++)
            {
                if ($newPaths[$i] == "..") unset($newPaths[$i]);
            }
           
            reset($newPaths);
           
            $stringNewPath = implode($stringExplode,$paths).
                $stringExplode.implode($stringExplode,$newPaths);
           
                return $stringNewPath;
        }
    }   
}

require_once(bugFixRequirePath("../config.php"));

gabe at websaviour dot com (14-Jul-2006 01:42)

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 04:35)

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 02:41)

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 (25-Feb-2006 05:34)

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 11:24)

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 08:08)

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 07:54)

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 06:42)

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 09:58)

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 06:29)

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 (22-Nov-2004 07:50)

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.