Detailed explanation of spl_autoload_register function

Before understanding this function, let’s look at another function: __autoload.

1. __autoload

This is an automatic loading function. In PHP5, when we instantiate an undefined class, this function will be triggered. Look at the following example:

printit.class.php 

<?php

.php

classprintit.class

 function

  echo ;

 }

}

?> 

index.php 

function __autoload( $class

class

PRINTIT {

 $file = $class . '.class.php';  

 if ( is_file($file

  require_once($file);  

 }

} 

$obj = new PRINTIT();

$obj->doPrint();

?>

运行index.php后正常输出hello world。在index.php中，由于没有包含printit.class.php，在实例化printit时，自动调用__autoload函数，参数$class的值即为类名printit，此时printit.class.php就被引进来了。  

在面向对象中这种方法经常使用，可以避免书写过多的引用文件，同时也使整个系统更加灵活。  

二、spl_autoload_register()  

再看spl_autoload_register()，这个函数与__autoload有与曲同工之妙，看个简单的例子：  

function loadprint( $class

function

doPrint() {

 $file = $class . '.class.php';  

 if (is_file($file

echo

  require_once($file);  

 } 

} 

spl_autoload_register( 'loadprint' ); 

;

$obj = new PRINTIT();'hello world'

🎜🎜🎜🎜🎜🎜🎜🎜🎜?> 🎜🎜 🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜index.php 🎜🎜🎜🎜🎜🎜🎜🎜🎜 🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜 🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜function🎜 🎜__autoload(🎜🎜$class🎜🎜) {🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜$file🎜🎜=🎜🎜$class🎜🎜. 🎜🎜'.class.php'🎜🎜; 🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜 🎜🎜if🎜🎜(🎜🎜is_file🎜🎜(🎜🎜$file🎜🎜) ) { 🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜 🎜🎜require_once🎜🎜(🎜🎜$file🎜🎜); 🎜🎜🎜🎜🎜🎜🎜 🎜🎜}🎜🎜🎜🎜🎜🎜🎜 🎜🎜🎜🎜🎜} 🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜 🎜= 🎜🎜new🎜 🎜PRINTIT();🎜🎜🎜🎜🎜🎜🎜🎜 🎜🎜🎜🎜$obj🎜🎜->doPrint();🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜?>🎜🎜🎜🎜🎜🎜🎜 🎜🎜After running index.php, hello world will be output normally. In index.php, since printit.class.php is not included, when instantiating printit, the __autoload function is automatically called. The value of the parameter $class is the class name printit. At this time, printit.class.php is introduced. . 🎜🎜This method is often used in object-oriented, which can avoid writing too many reference files and also make the entire system more flexible. 🎜🎜2. spl_autoload_register() 🎜🎜Look at spl_autoload_register() again. This function has the same effect as __autoload. Let’s look at a simple example: 🎜🎜🎜 🎜🎜 🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜function🎜 🎜loadprint( 🎜🎜$class🎜🎜) {🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜$file🎜🎜=🎜🎜$class🎜🎜. 🎜🎜'.class.php'🎜🎜; 🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜 🎜🎜if🎜🎜(🎜🎜is_file🎜🎜(🎜🎜$file🎜🎜)) { 🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜 🎜🎜require_once🎜🎜(🎜🎜$file🎜🎜); 🎜🎜🎜🎜🎜🎜 🎜🎜🎜🎜🎜🎜🎜🎜} 🎜🎜🎜🎜🎜🎜🎜🎜 🎜🎜🎜🎜} 🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜 🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜spl_autoload_register(🎜 🎜'loadprint'🎜🎜); 🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜 🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜$obj🎜 🎜= 🎜🎜new🎜 🎜PRINTIT();🎜🎜🎜🎜🎜

$obj->doPrint();

?>

将__autoload换成loadprint函数。但是loadprint不会像__autoload自动触发，这时spl_autoload_register()就起作用了，它告诉PHP碰到没有定义的类就执行loadprint()。 

spl_autoload_register() 调用静态方法 

class$obj->doPrint();

 public static function loadprint( $class?>

Replace __autoload with the loadprint function. But loadprint will not be triggered automatically like __autoload. At this time, spl_autoload_register() will work. It tells PHP to execute loadprint() when it encounters an undefined class.

spl_autoload_register() calls static method   $file = $class . '.class.php';  

  if (is_file($file

   require_once($file);  

  } 

 }

} 

array('test','loadprint'

test {

class

public

static

function$obj = new PRINTIT();

$obj->doPrint();

loadprint($class

?>

) {

🎜🎜🎜🎜🎜🎜 🎜🎜$file🎜🎜= 🎜🎜$class🎜🎜. 🎜🎜'.class.php'🎜🎜; 🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜 🎜🎜if🎜🎜(🎜🎜is_file🎜🎜(🎜🎜$file🎜🎜)) { 🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜 🎜🎜require_once🎜🎜(🎜🎜$file🎜🎜); 🎜🎜🎜🎜🎜🎜 🎜🎜🎜🎜🎜🎜 🎜🎜} 🎜🎜🎜🎜🎜🎜🎜🎜 🎜🎜🎜🎜 🎜🎜}🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜} 🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜 🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜spl_autoload_register( 🎜🎜array🎜🎜(🎜🎜'test'🎜🎜,🎜🎜'loadprint'🎜🎜) );🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜//Another way of writing: spl_autoload_register( "test::loadprint" ); 🎜PRINTIT();🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜 $obj🎜🎜->doPrint();🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜🎜?>🎜🎜🎜🎜🎜🎜🎜🎜 🎜 The above has introduced the detailed explanation of the spl_autoload_register function, including the relevant aspects. I hope it will be helpful to friends who are interested in PHP tutorials. 🎜 🎜 🎜