Laravel框架中composer自动加载的实现分析

require_once __DIR__ . '/composer' . '/autoload_real.php';
return ComposerAutoloaderInit7b20e4d61e2f88170fbbc44c70d38a1f::getLoader();

<?php
/**
 * Created by PhpStorm.
 * User: Administrator
 * Date: 2017/12/7
 * Time: 14:10
 */
namespace app;
class Autoload {

 public function __construct()
 {
  $this->autoload();
 }
 public function autoload(){
  // spl_autoload_register(array('Autoload','ss'),true); 会触发致命错误，必须带上命名空间
  spl_autoload_register(array('app\Autoload','ss'),true);
 }
 public function ss(){
  echo 666;
  exit;
 }
}

<?php
/**
 * Created by PhpStorm.
 * User: Administrator
 * Date: 2017/12/7
 * Time: 14:10
 */
require 'autoload.php';
$autoload=new \app\Autoload();
$b=new B();// 此时自动运行自动加载函数
echo 77;
exit;

 public static function getLoader()
 {
  if (null !== self::$loader) {
   return self::$loader;
  }
  //注册自动加载函数，在加载或实例化类，运行loadClassLoader函数
  spl_autoload_register(array('ComposerAutoloaderInit7b20e4d61e2f88170fbbc44c70d38a1f', 'loadClassLoader'), true, true);
  self::$loader = $loader = new \Composer\Autoload\ClassLoader();
  spl_autoload_unregister(array('ComposerAutoloaderInit7b20e4d61e2f88170fbbc44c70d38a1f', 'loadClassLoader'));
/********************1********************************************************
  $map = require __DIR__ . '/autoload_namespaces.php';
  foreach ($map as $namespace => $path) {
   $loader->set($namespace, $path);
  }
  $map = require __DIR__ . '/autoload_psr4.php';
  foreach ($map as $namespace => $path) {
   $loader->setPsr4($namespace, $path);
  }
  $classMap = require __DIR__ . '/autoload_classmap.php';
  if ($classMap) {
   $loader->addClassMap($classMap);
  }
/********************1********************************************************
  $loader->register(true);  $includeFiles = require __DIR__ . '/autoload_files.php';  foreach ($includeFiles as $fileIdentifier => $file) {   composerRequire7b20e4d61e2f88170fbbc44c70d38a1f($fileIdentifier, $file);  }  return $loader; }}

public function register($prepend = false)
{
 spl_autoload_register(array($this, 'loadClass'), true, $prepend);
}

public function findFile($class)
{
/// 特别注意 参数$class 是根据命名空间生成的class名称，具体请参考命名空间特性。
 // work around for PHP 5.3.0 - 5.3.2 https://bugs.php.net/50731
 if ('\\' == $class[0]) {
  $class = substr($class, 1);
 }
 // class map lookup 首先从加载的classMap 中寻找
 if (isset($this->classMap[$class])) {
  return $this->classMap[$class];
 }
 if ($this->classMapAuthoritative) {
  return false;
 }
// 从刚才加载的配置文件中寻找文件。先按照 psr4 规则寻找，再按照psr0 寻找
// 两种规则的不同主要是对下划线的处理方式。
 $file = $this->findFileWithExtension($class, '.php');
 // Search for Hack files if we are running on HHVM
 if ($file === null && defined('HHVM_VERSION')) {
  $file = $this->findFileWithExtension($class, '.hh');
 }
 if ($file === null) {
  // Remember that this class does not exist.
  return $this->classMap[$class] = false;
 }
 return $file;
}

$includeFiles = require __DIR__ . '/autoload_files.php';
foreach ($includeFiles as $fileIdentifier => $file) {
 composerRequire7b20e4d61e2f88170fbbc44c70d38a1f($fileIdentifier, $file);
}