PHP 7.1.20 Released

include_once

(PHP 4, PHP 5, PHP 7)

Выражение include_once включает и выполняет указанный файл во время выполнения скрипта. Его поведение идентично выражению include, с той лишь разницей, что если код из файла уже один раз был включен, он не будет включен и выполнен повторно и вернёт TRUE. Как видно из имени, он включит файл только один раз.

include_once может использоваться в тех случаях, когда один и тот же файл может быть включен и выполнен более одного раза во время выполнения скрипта, в данном случае это поможет избежать проблем с переопределением функций, переменных и т.д.

Смотрите документацию по include для получения информации о том, как эта функция работает.

Замечание:

В PHP 4 функциональность _once отличалась в регистронезависимых операционных системах (таких как Windows), к примеру:

Пример #1 Пример include_once в регистронезависимых ОС для PHP 4

<?php
include_once "a.php"// это подключит a.php
include_once "A.php"// это подключит a.php снова! (только в PHP 4)
?>

Это поведение изменилось в PHP 5. К примеру, пути в Windows сначала нормализуются так, чтобы C:\PROGRA~1\A.php обозначало то же самое, что и C:\Program Files\a.php, и файл включается только один раз.

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User Contributed Notes 8 notes

up
102
Greg McCarthy
1 year ago
In response to what a user wrote 8 years ago regarding include_once being ran two times in a row on a non-existent file:

Perhaps 8 years ago that was the case, however I have tested in PHP 5.6, and I get this:

$result = include_once 'fakefile.php';  // $result = false
$result = include_once 'fakefile.php'   // $result is still false
up
190
roach dot scott+spam at googlemail dot com
10 years ago
If you include a file that does not exist with include_once, the return result will be false.

If you try to include that same file again with include_once the return value will be true.

Example:
<?php
var_dump
(include_once 'fakefile.ext'); // bool(false)
var_dump(include_once 'fakefile.ext'); // bool(true)
?>

This is because according to php the file was already included once (even though it does not exist).
up
-17
xcl_rockman at qq dot com
3 years ago
config.php
<?php
return array("test">1);

-------------
//first
$config = include_once("config.php");
var_dump($config);

$config = include_once("config.php");
var_dump($config);

-------------------
output will be
array(
   
"test"=>1,
)

nothing
up
-12
sascha dot diebel at gmail dot com
1 year ago
i tried

-------------------------------- index.php:
$out='todo 1';
include 'file1.php';
$out='todo 2';
include 'file1.php';
echo 'end';
-------------------------------- file1.php:
include_once 'file2.php';
if(isset($out)){
echo $out;
}
-------------------------------- file2.php:
$out='first todo once';
include 'file.php';

the output is:
first todo once
first todo once
todo 2

what should i do?

if i would replace in file2.php include with include_once, then i have following output:
first todo once
todo 2

i could write
$out='first todo once';
include 'file1.php'
$out='todo 1';
include 'file1.php';
$out='todo 2';
include 'file1.php';

but i don't want :-)
please help
up
-47
flobee at gmail dot com
13 years ago
i already had a discussion with several people about "not shown errors"
error reporting and all others in php.ini set to: "show errors" to find problems:
the answer i finally found:
if you have an "@include..." instead of "include..." or "require..('somthing') in any place in your code
all following errors are not shown too!!!

so, this is actually a bad idea when developing because paser errors will be droped too:
<?php
if(!@include_once('./somthing') ) {
    echo
'can not include';
}
?>

solution:
<?php
if(!@file_exists('./somthing') ) {
    echo
'can not include';
} else {
   include(
'./something');
}
?>
up
-50
webmaster AT domaene - kempten DOT de
11 years ago
Since I like to reuse a lot of code it came handy to me to begin some sort of library that I stored in a subdir
e.g. "lib"

The only thing that bothered me for some time was that although everything worked all IDEs reported during editing
these useless warnings "file not found" when library files included other library files, since my path were given all relative to the corresponding document-root.

Here is a short workaround that makes that gone:

<?php
// Change to your path

if(strpos(__FILE__,'/lib/') != FALSE){
   
chdir("..");
}
include_once (
'./lib/other_lib.inc');
// ... or any other include[_once] / require[_once]
?>

just adjust the path and it will be fine - also for your IDE.

greetings
up
-61
emanuele at rogledi dot com
10 years ago
For include_once a file in every paths of application we can do simply this

include_once($_SERVER["DOCUMENT_ROOT"] . "mypath/my2ndpath/myfile.php");
up
-35
1083706899 at qq dot com
2 years ago
require_once() can check the file if once include ,or the file is wrong will tell a error and quit the script.
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