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    include_once

    (PHP 4, PHP 5, PHP 7, PHP 8)

    include_once 命令は、スクリプトの実行時に指定 したファイルを読み込み評価します。この動作は、 include 命令と似ていますが、ファイルからのコー ドが既に読み込まれている場合は、再度読み込まれないという重要な違い があります。また、include_once は true を返します。その名が示す通り、ファイルは一度しか読み込まれません。

    include_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。

    この関数の動作についての情報は include のドキュメントを参照ください。

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    User Contributed Notes 10 notes

    up
    139
    Greg McCarthy
    7 years 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
    176
    roach dot scott+spam at googlemail dot com
    16 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
    3
    Ben F
    5 years ago
    This currently (running latest PHP 7.4 NTS as of this writing, on Windows) returns as expected... false no matter how many times you include an inaccessible file, true if you include it more than once.
    up
    2
    mho
    5 years ago
    once i wrote script to include multiple files at once from a given location:

    function include_load($path)
        {
        foreach(glob($path . "/*.php") as $file)
            include_once($file);
        }

    last week i modified my code and merged all include files into one single file. this results in five times faster code. i have to mention, i am talking about +100 files to include where each file includes single function and filename is equal to function-name.
    up
    -34
    xcl_rockman at qq dot com
    9 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
    -27
    sascha dot diebel at gmail dot com
    7 years 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
    -53
    flobee at gmail dot com
    19 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
    -59
    webmaster AT domaene - kempten DOT de
    18 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
    -46
    1083706899 at qq dot com
    9 years ago
    require_once() can check the file if once include ,or the file is wrong will tell a error and quit the script.
    up
    -77
    emanuele at rogledi dot com
    16 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");
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