The role of php entry file

The role of the php entry file

The php entry file can realize the automatic loading function.

Parse the automatic loading function of PHP entry file

Automatic loading of php:

Before php5, we had to use a certain class or class Method, it must include or require before it can be used. Every time you use a class, you need to write an include. Please

php. The author wants to make it simple. It is best to reference a class. If there is no include currently, , the system can automatically find this class and automatically introduce it~

So: the __autoload() function came into being.

Usually placed in the application entry class, such as discuz, placed in class_core.php.

Recommended: "PHP Tutorial"

Let’s talk about a simple example first:

The first situation: the content of file A.php is as follows

<?php
class A{
　　public function __construct(){
　　       echo &#39;fff&#39;;
　　}
}
?>

The content of the file C.php is as follows:

<?php  
function __autoload($class)  
{  
$file = $class . &#39;.php&#39;;  
if (is_file($file)) {  
require_once($file);  
}  
}  
 
$a = new A(); //这边会自动调用__autoload，引入A.php文件
 
?>

Second case: Sometimes I hope to customize autoload and want to make a newer Cool name loader, then C.php is changed to the following:

<?php
function loader($class)
{
$file = $class . &#39;.php&#39;;
if (is_file($file)) {
require_once($file);
}
}
spl_autoload_register(&#39;loader&#39;); //注册一个自动加载方法，覆盖原有的__autoload
$a = new A();
?>

The third situation: I hope to be more sophisticated and use a class to manage automatic loading

<?php  
class Loader  
{  
public static function loadClass($class)  
{  
$file = $class . &#39;.php&#39;;  
if (is_file($file)) {  
require_once($file);  
}  
}  
}  
 
spl_autoload_register(array(&#39;Loader&#39;, &#39;loadClass&#39;));  
 
$a = new A();
 
?>

Currently the best form.

Usually we put spl_autoload_register(*) in the entry script, that is, quoted from the beginning. For example, the following discuz approach.

if(function_exist('spl_autoload_register')){
 
　　spl_autoload_register(array('core','autoload'));  //如果是php5以上，存在注册函数，则注册自己写的core类中的autoload为自动加载函数
 
}else{
 
　　function __autoload($class){         //如果不是，则重写php原生函数__autoload函数，让其调用自己的core中函数。
 
　　　　return core::autoload($class);
 
　　}
 
}

This paragraph is thrown at the front of the entry file, which is naturally excellent~

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