__autoload
(PHP 5)
__autoload — Attempt to load undefined class
Description
void __autoload
( string
$class
)You can define this function to enable classes autoloading.
Parameters
-
class -
Name of the class to load
Return Values
No value is returned.
- PHP Руководство
- Функции по категориям
- Индекс функций
- Справочник функций
- Расширения, относящиеся к переменным и типам
- Функции работы с классами и объектами
- __autoload
- call_user_method_array
- call_user_method
- class_alias
- class_exists
- get_called_class
- get_class_methods
- get_class_vars
- get_class
- get_declared_classes
- get_declared_interfaces
- get_declared_traits
- get_object_vars
- get_parent_class
- interface_exists
- is_a
- is_subclass_of
- method_exists
- property_exists
- trait_exists
Коментарии
Even I have never been using this function, just a simple example in order to explain it;
./myClass.php
<?php
class myClass {
public function __construct() {
echo "myClass init'ed successfuly!!!";
}
}
?>
./index.php
<?php
// we've writen this code where we need
function __autoload($classname) {
$filename = "./". $classname .".php";
include_once($filename);
}
// we've called a class ***
$obj = new myClass();
?>
*** At this line, our "./myClass.php" will be included! This is the magic that we're wondering... And you get this result "myClass init'ed successfuly!!!".
So, if you call a class that named as myClass then a file will be included myClass.php if it exists (if not you get an include error normally). If you call Foo, Foo.php will be included, and so on...
And you don't need some code like this anymore;
<?php
include_once("./myClass.php");
include_once("./myFoo.php");
include_once("./myBar.php");
$obj = new myClass();
$foo = new myFoo();
$bar = new myBar();
?>
Your class files will be included "automatically" when you call (init) them without these functions: "include, include_once, require, require_once".
If you can keep file name and class name as same, it will be good programming practice. It helps to __autoload function to load file without checking any condition.
function __autoload($class){
require_once( $class.".php");
}
It is highly recommended not to use the __autoload() function any more. Now the spl_autoload_register() function is what you should consider.<?php
if(!function_exists('classAutoLoader')){
function classAutoLoader($class){
$class=strtolower($class);
$classFile=$_SERVER['DOCUMENT_ROOT'].'/include/class/'.$class.'.class.php';
if(is_file($classFile)&&!class_exists($class)) include $classFile;
}
}
spl_autoload_register('classAutoLoader');
?>
Guys, this document ( i mean __autoload() ) not mentioned one special situation: if you both use __autoload() and spl_autoload_register(), the __autoload() function will never to be called. Although spl_autoload_register() documentation explained why, i decide to wrote this in case some one get confused and waste all day to figure out why.
Here is some code to verify above:
<?php
function __autoload($class) {
}
function my_loader() {
}
function your_loader() {
}
var_dump ( spl_autoload_functions () );
echo '<br/>';
spl_autoload_register ( 'my_loader' );
spl_autoload_register ( 'your_loader' );
var_dump ( spl_autoload_functions () );
You should use include() or require() inside __autoload()
instead of include_once() or require_once().
If you reach __autoload(), then you know the file with the class definition has not been loaded yet.
include() and require() are more efficient than include_once() and require_once().
In PHP 7.2, this code will trigger a "Deprecated: __autoload() is deprecated, use spl_autoload_register() instead in path\to\file.php on line *" error although the spl_autoload_register function really really exists.
<?php
if(!function_exists('spl_autoload_register')){
function __autoload($class){
// blah blah blah
}
}
?>
We you create an object of the class and If the PHP engine doesn't find the class file included in the script then __autoload() magic method will automatically trigger.
You can implement it as given below example:
<?PHP
function __autoload($ClassName)
{
include($ClassName.".php");
}
$obj = new Base;
?>