PHP automatic loading mechanism _php tutorial

First, the method of implementing automatic loading in PHP

Use Require,include,require_once,include_once to load manually.

Use __autoload for automatic loading
Automatic loading using SPL's AutoLoad
Implementation of manual loading:

When there are few files to load, we can use the first one to complete. It's easy and it's no problem.

[PHP]
Require_once ' a.php ';
Require_once ' b.php ';
Require_once ' c.php ';

Require_once ' a.php ';
Require_once ' b.php ';
Require_once ' c.php ';
But is this OK when you need to load a lot of files? What do we do when we need to write 10, 20 require_once or more?

At this point we can use the __autoload method to simplify our code.

Implementation of __autoload Loading:

We create a in.php file in the test directory, which reads as follows.

[PHP]
Echo ' I am the in.php under test
';

Echo ' I am the in.php under test
'; then create a loader.php in the test directory, as follows.

[PHP]
You need to overload the __autoload method to customize the path that contains the class file
function __autoload ($classname)
{
$class _file = Strtolower ($classname). ". PHP ";
if (file_exists ($class _file)) {
Require_once ($class _file);
}
}
@ $test = new in (); Execution here will output I'm the in.php under test

You need to overload the __autoload method to customize the path that contains the class file
function __autoload ($classname)
{
$class _file = Strtolower ($classname). ". PHP ";
if (file_exists ($class _file)) {
Require_once ($class _file);
}
}
@ $test = new in (); Execution here will output I'm the in.php under test no problem, success! We can also create additional files to load, but what do you do when you need a lot of files to separate directories?

At this point we need to modify the loader.php to use the mapping to find the file to be loaded.

[PHP]
function __autoload ($class _name) {
$map = Array (
' Index ' = './include/index.php ',
' In ' = './in.php '
);

if (file_exists ($map [$class _name]) && isset ($map [$class _name]) {
Require_once $map [$class _name];
}
}
New index ();

function __autoload ($class _name) {
$map = Array (
' Index ' = './include/index.php ',
' In ' = './in.php '
);

if (file_exists ($map [$class _name]) && isset ($map [$class _name]) {
Require_once $map [$class _name];
}
}
New index ();

The advantage of this approach is that the class name and file path are only maintained with a single map, so when the file structure changes, you do not need to modify the class name, just modify the corresponding item in the map.

But __autoload can only be used once in a project, when your project refers to someone else's project, there is a __autoload in your project, and someone else's project has a __autoload, so two __autoload conflict. The solution is to modify __ AutoLoad become a, this is undoubtedly very cumbersome, application scenario single.

The AutoLoad load implementation of SPL:

SPL's AutoLoad series functions use a autoload call stack, and you can use Spl_autoload_register to register multiple custom autoload functions with a wide range of application scenarios

Related functions for automatic loading of SPL
Spl_autoload is the default implementation of _autoload (), which will go to Include_path to find $class_name (. php/.inc) Spl_autoload for automatic loading:
Create the in.php in the test directory as follows:

[PHP]
Class in {
Public Function index () {
Echo ' I am the in.php under test ';
}
}
?>

Class in {
Public Function index () {
Echo ' I am the in.php under test ';
}
}
?> in the test directory to establish the loader.php, the content is as follows
[HTML]
Set_include_path ("/var/www/test/"); Here you need to put the path into the include
Spl_autoload ("in"); Find/var/www/test/in.php
$in = new in ();
$in->index ();

Set_include_path ("/var/www/test/"); Here you need to put the path into the include
Spl_autoload ("in"); Find/var/www/test/in.php
$in = new in ();
$in->index ();
Spl_autoload_register registers the function with the SPL __autoload function stack and modifies the loader.php
[PHP]
function AutoLoad ($class) {
if ($class = = ' in ') {
Require_once ("/var/www/test/in.php");
}
}
Spl_autoload_register (' AutoLoad ');
$a = new in ();
$a->index ();

function AutoLoad ($class) {
if ($class = = ' in ') {
Require_once ("/var/www/test/in.php");
}
}
Spl_autoload_register (' AutoLoad ');
$a = new in ();
$a->index ();

Spl_autoload_register registering multiple custom autoload function applications
First build the Mods folder in the test directory and set up the inmod.mod.php content as follows:
[PHP]
Class Inmod
{
function __construct ()
{
Echo ' I am in ' under mods;
}
}

Class Inmod
{
function __construct ()
{
Echo ' I am in ' under mods;
}
}
Then create the Libs folder in the test directory and build the inlib.lib.php content as follows:
[PHP]
Class Inlib
{
function __construct ()
{
Echo ' I am libs under ';
}
}

Class Inlib
{
function __construct ()
{
Echo ' I am libs under ';
}
Finally, build the loader.php content in the test directory as follows
[PHP]
Class Loader {
/**
* Auto Load Class
* @param $class class name
*/
public static function mods ($class) {
if ($class) {
Set_include_path ("/var/www/test/mods/");
Spl_autoload_extensions (". mod.php");
Spl_autoload (Strtolower ($class));
}
}
public static function libs ($class) {
if ($class) {
Set_include_path ("/var/www/test/libs/");
Spl_autoload_extensions (". lib.php");
Spl_autoload (Strtolower ($class));
}
}
}
Spl_autoload_register (Array (' Loader ', ' mods '));
Spl_autoload_register (Array (' Loader ', ' Libs '));
New Inmod ();//OutputI'm under mods.
New Inlib ();//OutputI'm libs under.

Class Loader {
/**
* Auto Load Class
* @param $class class name
*/
public static function mods ($class) {
if ($class) {
Set_include_path ("/var/www/test/mods/");
Spl_autoload_extensions (". mod.php");
Spl_autoload (Strtolower ($class));
}
}
public static function libs ($class) {
if ($class) {
Set_include_path ("/var/www/test/libs/");
Spl_autoload_extensions (". lib.php");
Spl_autoload (Strtolower ($class));
}
}
}
Spl_autoload_register (Array (' Loader ', ' mods '));
Spl_autoload_register (Array (' Loader ', ' Libs '));
New Inmod ();//Output I'm under mods.
New Inlib ();//Output I am libs under

http://www.bkjia.com/PHPjc/477470.html www.bkjia.com true http://www.bkjia.com/PHPjc/477470.html techarticle first, the method of automatic loading in PHP is loaded manually using Require,include,require_once,include_once. Use __autoload to automatically load autoload using SPL to implement ...

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