require_once
Need some help please. I keep getting this error:
can not include
Fatal error: Cannot redeclare get_postdata()
Here's the solution I was told to put in, but it's not working
<?php
if(!@file_exists('deprecated.php') ) {
echo 'can not include';
} else {
include('deprecated.php');
}
* @package WordPress
* @subpackage Deprecated
*/
include_once
The include_once 语句在脚本执行期间包含并运行指定文件。此行为和 include 语句类似，唯一区别是如果该文件中的代码已经被包含了，则不会再次包含。如同此语句名字暗示的那样，只会包含一次。
include_once 应该用于在脚本执行期间同一个文件有可能被包含超过一次的情况下，想确保它只被包含一次以避免函数重定义，变量重新赋值等问题。
返回值和 include 相同。如果文件已被包含，本函数返回 TRUE。
Note:
在PHP4中，要注意 include_once 和 require_once 在大小写不敏感的操作系统中（例如 Windows）的行为可能不是所期望的。
Example #1 include_once 在 Windows 下不区分大小写
<?php
include_once "a.php"; // this will include a.php
include_once "A.php"; // this will include a.php again on Windows! (PHP 4 only)
?>此行为在 PHP 5 中改了，路径先被规格化，因此 C:\PROGRA~1\A.php 和 C:\Program Files\a.php 的实现一样，文件只会被包含一次。
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User Contributed Notes
include_once
Frankbrennanfilms at yahoo dot com
21-Sep-2010 01:43
nospam at freeproxylist dot org
30-Mar-2009 08:51
I would like to share one very useful tip with include_* statements. For example we have two classes first.class.php and second.class.php both located in the same directory (./classes) and first one uses the second one. So we have:
first.class.php
<?php
include_once './second.class.php';
...
?>
also we have file which uses first.class.php:
<?php
include_once './classes/first.class.php';
...
?>
if you will try to execute your script you will get error. Reason: the current directory is different and the relative path in first.class.php (./second.class.php) will be incorrect.
Here is two possible solution I have found:
<?php
include_once dirname(__FILE__).'/second.class.php';
...
?>
or
<?php
chdir(dirname(__FILE__));
include_once './second.class.php';
...
?>
Hope that tip will be useful for some other software developer
Admin of http://FreeProxyList.org
neil at holcomb dot com
07-Jan-2009 01:42
Using include_once() in the __autoload() function is redundant. __autoload() is only called when php can't find your class definition. If your file containg your class was already included, the class defenition would already be loaded and __autoload() would not be called. So save a little overhead and only use include() within __autoload()
Neil Holcomb
roach dot scott+spam at googlemail dot com
27-Jun-2008 05:22
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).
emanuele at rogledi dot com
18-May-2008 05:40
For include_once a file in every paths of application we can do simply this
include_once($_SERVER["DOCUMENT_ROOT"] . "mypath/my2ndpath/myfile.php");
php at metagg dot com
08-Aug-2007 03:29
If you are like me and make heavy use of the __autoload magic function, always set include paths so you can just instantiate your class, and have multiple locations and name schemes for your custom libraries then you might be frustrated by simple parse errors being supressed when using @include_once('lib.php').
The solution I came up with was:
define('IN_PRODUCTION_ENV',FALSE);
function __autoload($class){
$paths = array();
$paths[] = "{$class}_lib.php";
$paths[] = "{$class}_inc.php";
$paths[] = "{$class}.php";
if(IN_PRODUCTION_ENV){
foreach($paths as &$path){
if((@include_once $path) !== false){ return; }//if
}//foreach
}else{
// we are not in a production environment so we want to see all errors...
$include_paths = explode(PATH_SEPARATOR,get_include_path());
foreach($include_paths as $include_path){
// go through each of the different class names...
foreach($paths as $path){
// attach each class name to the include path...
$include_file = $include_path.$path;
if(file_exists($include_file)){
if((include_once $include_file) !== false){ return; }//if
}//if
}//foreach
}//foreach
}//if/else
trigger_error("{$class} was not found",E_USER_ERROR);
}//method
Now, just make sure you define IN_PRODUCTION_ENV to true or false to get either the slower (with all parse errors shown) or the faster (just suppress everything) autoloading. Hope this helps someone else since it was annoying just having blank screens show up when I had a simple parse error. Thanks to flobee at gmail dot com for providing me with the epiphany on why pages were showing up blank...-Metagg
webmaster AT domaene - kempten DOT de
10-Aug-2006 05:11
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
29-Aug-2005 01:52
Dealing with function redefinitions
include_once and require_once are very useful if you have a library of common functions. If you try to override with - that is define - an identically named local function however, PHP will halt noting that it cannot redeclare functions. You can allow for this by bracketing (within the include file):
function myUsefulFunc($arg1, $arg2) {
... }
with
if (!function_exists('myUsefulFunc')) {
function myUsefulFunc($arg1, $arg2) {
... }}
Top level functions (ie. those not defined within other functions or dependent on code running) in the local file are always parsed first, so http://php.net/function_exists within the included/required file is safe - it doesn't matter where the include statements are in the local code.
Csaba Gabor from Vienna
flobee at gmail dot com
26-May-2005 07:55
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');
}
?>
Pure-PHP
17-Mar-2005 02:17
Inlude_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
include_once("includeWrapper.class.php")
includeWrapper::includeOnce("Class1.class.php");
includeWrapper::requireOnce("Class1.class.php");
includeWrapper::includeOnce("Class2.class.php")
bioster at peri dot csclub dot uwaterloo dot ca
28-Oct-2004 03:06
Something to be wary of: When you use include_once and the data that you include falls out of scope, if you use include_once again later it will not include despite the fact that what you included is no longer available.
So you should be wary of using include_once inside functions.