(PHP 4, PHP 5, PHP 7)
The include_once statement includes and evaluates
the specified file during the execution of the script.
This is a behavior similar to the include statement,
with the only difference being that if the code from a file has already
been included, it will not be included again, and include_once returns TRUE. As the name suggests,
the file will be included just once.
include_once may be used in cases where the same file might be included and evaluated more than once during a particular execution of a script, so in this case it may help avoid problems such as function redefinitions, variable value reassignments, etc.
See the include documentation for information about how this function works.
add a note
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' // $result is still false
If you include a file that does not exist with include_once, the return result will be false.
If you try to include that same file again with include_once the return value will be true.
Example:
<?php
var_dump(include_once 'fakefile.ext'); // bool(false)
var_dump(include_once 'fakefile.ext'); // bool(true)
?>
This is because according to php the file was already included once (even though it does not exist).
once i wrote script to include multiple files at once from a given location:
function include_load($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.
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
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';
$out='todo 2';
include 'file1.php';
but i don't want :-)
please help
Since I like to reuse a lot of code it came handy to me to begin some sort of library that I stored in a subdir
e.g. "lib"
The only thing that bothered me for some time was that although everything worked all IDEs reported during editing
these useless warnings "file not found" when library files included other library files, since my path were given all relative to the corresponding document-root.
Here is a short workaround that makes that gone:
<?php
// Change to your path
if(strpos(__FILE__,'/lib/') != FALSE){
chdir("..");
}
include_once ('./lib/other_lib.inc');
// ... or any other include[_once] / require[_once]
?>
just adjust the path and it will be fine - also for your IDE.
greetings
i already had a discussion with several people about "not shown errors"
error reporting and all others in php.ini set to: "show errors" to find problems:
the answer i finally found:
if you have an "@include..." instead of "include..." or "require..('somthing') in any place in your code
all following errors are not shown too!!!
so, this is actually a bad idea when developing because paser errors will be droped too:
<?php
if(!@include_once('./somthing') ) {
echo 'can not include';
}
?>
solution:
<?php
if(!@file_exists('./somthing') ) {
echo 'can not include';
} else {
include('./something');
}
?>
require_once() can check the file if once include ,or the file is wrong will tell a error and quit the script.
For include_once a file in every paths of application we can do simply this
include_once($_SERVER["DOCUMENT_ROOT"] . "mypath/my2ndpath/myfile.php");
