autoload-psr规范代码

大家都知道,当我们想在文件A中使用文件B中的某个类或方法时,必然需要将文件B通过include或者require等函数或语句引进来。为此不知道PHP哪个版本中出现了个魔术方法__autoload(),这个函数将会在创建一个对象的时候自动调用,所以我们只需要在__autoload()函数中写入类似于下面的代码就可以保证,使用什么就包含什么。
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class Example(){
function __autoload($className){
require $className.’.php’;
}
}
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但是当项目越来越大,文件越来越多,类越来越混乱的时候,单单通过require和include的方式就会感到疲倦不堪,你可能会说只要都是用include_once或者require_once就可以保证只需引入一次,这样就能保证文件引入不会重复了,但如果有好的方式实现干嘛不用呢?为此出现了如Namespace和spl_autoload_register()等方式来更好做好PHP的autoload工作。

而目前通过composer来进行包管理工作时也将自动加载做到了通用化与自动化,所以来看下composer是如何来进行autoload的。

composer典型的autoload目录结构
D03AAD3F-0B24-49A2-8C2F-1A0021383009

通常自动加载都是从require ‘autoload.php’;开始的,下面来看composer的类自动加载过程。
1.autoload.php
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$path) {
$loader->set($namespace, $path);
}
/*
加载使用最新版autoload的Psr4
*/
$map = require __DIR__ . ‘/autoload_psr4.php’;
foreach ($map as $namespace => $path) {
$loader->setPsr4($namespace, $path);
}
/*
获得类的Map数组,然后spl_autoload_register
*/
$classMap = require __DIR__ . ‘/autoload_classmap.php’;
if ($classMap) {
$loader->addClassMap($classMap);
}
$loader->register(true);

return $loader;
}
}

function composerRequired372782b3e1f4bbef6a945ee27441d36($file)
{
require $file;
}
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ClassLoader类是composer自动加载的核心
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* Jordi Boggiano
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*/

namespace Composer\Autoload;

/**
* ClassLoader implements a PSR-0 class loader
*
* See https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-0.md
*
* $loader = new \Composer\Autoload\ClassLoader();
*
* // register classes with namespaces
* $loader->add(‘Symfony\Component’, __DIR__.’/component’);
* $loader->add(‘Symfony’, __DIR__.’/framework’);
*
* // activate the autoloader
* $loader->register();
*
* // to enable searching the include path (eg. for PEAR packages)
* $loader->setUseIncludePath(true);
*
* In this example, if you try to use a class in the Symfony\Component
* namespace or one of its children (Symfony\Component\Console for instance),
* the autoloader will first look for the class under the component/
* directory, and it will then fallback to the framework/ directory if not
* found before giving up.
*
* This class is loosely based on the Symfony UniversalClassLoader.
*
* @author Fabien Potencier
* @author Jordi Boggiano
*/
class ClassLoader
{
// PSR-4
private $prefixLengthsPsr4 = array();
private $prefixDirsPsr4 = array();
private $fallbackDirsPsr4 = array();

// PSR-0
private $prefixesPsr0 = array();
private $fallbackDirsPsr0 = array();

private $useIncludePath = false;
private $classMap = array();

private $classMapAuthoritative = false;

public function getPrefixes()
{
if (!empty($this->prefixesPsr0)) {
return call_user_func_array(‘array_merge’, $this->prefixesPsr0);
}

return array();
}

public function getPrefixesPsr4()
{
return $this->prefixDirsPsr4;
}

public function getFallbackDirs()
{
return $this->fallbackDirsPsr0;
}

public function getFallbackDirsPsr4()
{
return $this->fallbackDirsPsr4;
}

public function getClassMap()
{
return $this->classMap;
}

/**
* @param array $classMap Class to filename map
*/
public function addClassMap(array $classMap)
{
if ($this->classMap) {
$this->classMap = array_merge($this->classMap, $classMap);
} else {
$this->classMap = $classMap;
}
}

/**
* Registers a set of PSR-0 directories for a given prefix, either
* appending or prepending to the ones previously set for this prefix.
*
* @param string $prefix The prefix
* @param array|string $paths The PSR-0 root directories
* @param bool $prepend Whether to prepend the directories
*/
public function add($prefix, $paths, $prepend = false)
{
if (!$prefix) {
if ($prepend) {
$this->fallbackDirsPsr0 = array_merge(
(array) $paths,
$this->fallbackDirsPsr0
);
} else {
$this->fallbackDirsPsr0 = array_merge(
$this->fallbackDirsPsr0,
(array) $paths
);
}

return;
}

$first = $prefix[0];
if (!isset($this->prefixesPsr0[$first][$prefix])) {
$this->prefixesPsr0[$first][$prefix] = (array) $paths;

return;
}
if ($prepend) {
$this->prefixesPsr0[$first][$prefix] = array_merge(
(array) $paths,
$this->prefixesPsr0[$first][$prefix]
);
} else {
$this->prefixesPsr0[$first][$prefix] = array_merge(
$this->prefixesPsr0[$first][$prefix],
(array) $paths
);
}
}

/**
* Registers a set of PSR-4 directories for a given namespace, either
* appending or prepending to the ones previously set for this namespace.
*
* @param string $prefix The prefix/namespace, with trailing ‘\\’
* @param array|string $paths The PSR-0 base directories
* @param bool $prepend Whether to prepend the directories
*
* @throws \InvalidArgumentException
*/
public function addPsr4($prefix, $paths, $prepend = false)
{
if (!$prefix) {
// Register directories for the root namespace.
if ($prepend) {
$this->fallbackDirsPsr4 = array_merge(
(array) $paths,
$this->fallbackDirsPsr4
);
} else {
$this->fallbackDirsPsr4 = array_merge(
$this->fallbackDirsPsr4,
(array) $paths
);
}
} elseif (!isset($this->prefixDirsPsr4[$prefix])) {
// Register directories for a new namespace.
$length = strlen($prefix);
if (‘\\’ !== $prefix[$length – 1]) {
throw new \InvalidArgumentException(“A non-empty PSR-4 prefix must end with a namespace separator.”);
}
$this->prefixLengthsPsr4[$prefix[0]][$prefix] = $length;
$this->prefixDirsPsr4[$prefix] = (array) $paths;
} elseif ($prepend) {
// Prepend directories for an already registered namespace.
$this->prefixDirsPsr4[$prefix] = array_merge(
(array) $paths,
$this->prefixDirsPsr4[$prefix]
);
} else {
// Append directories for an already registered namespace.
$this->prefixDirsPsr4[$prefix] = array_merge(
$this->prefixDirsPsr4[$prefix],
(array) $paths
);
}
}

/**
* Registers a set of PSR-0 directories for a given prefix,
* replacing any others previously set for this prefix.
*
* @param string $prefix The prefix
* @param array|string $paths The PSR-0 base directories
*/
public function set($prefix, $paths)
{
if (!$prefix) {
$this->fallbackDirsPsr0 = (array) $paths;
} else {
$this->prefixesPsr0[$prefix[0]][$prefix] = (array) $paths;
}
}

/**
* Registers a set of PSR-4 directories for a given namespace,
* replacing any others previously set for this namespace.
*
* @param string $prefix The prefix/namespace, with trailing ‘\\’
* @param array|string $paths The PSR-4 base directories
*
* @throws \InvalidArgumentException
*/
public function setPsr4($prefix, $paths)
{
if (!$prefix) {
$this->fallbackDirsPsr4 = (array) $paths;
} else {
$length = strlen($prefix);
if (‘\\’ !== $prefix[$length – 1]) {
throw new \InvalidArgumentException(“A non-empty PSR-4 prefix must end with a namespace separator.”);
}
$this->prefixLengthsPsr4[$prefix[0]][$prefix] = $length;
$this->prefixDirsPsr4[$prefix] = (array) $paths;
}
}

/**
* Turns on searching the include path for class files.
*
* @param bool $useIncludePath
*/
public function setUseIncludePath($useIncludePath)
{
$this->useIncludePath = $useIncludePath;
}

/**
* Can be used to check if the autoloader uses the include path to check
* for classes.
*
* @return bool
*/
public function getUseIncludePath()
{
return $this->useIncludePath;
}

/**
* Turns off searching the prefix and fallback directories for classes
* that have not been registered with the class map.
*
* @param bool $classMapAuthoritative
*/
public function setClassMapAuthoritative($classMapAuthoritative)
{
$this->classMapAuthoritative = $classMapAuthoritative;
}

/**
* Should class lookup fail if not found in the current class map?
*
* @return bool
*/
public function isClassMapAuthoritative()
{
return $this->classMapAuthoritative;
}

/**
* Registers this instance as an autoloader.
*
* @param bool $prepend Whether to prepend the autoloader or not
*/
public function register($prepend = false)
{
spl_autoload_register(array($this, ‘loadClass’), true, $prepend);
}

/**
* Unregisters this instance as an autoloader.
*/
public function unregister()
{
spl_autoload_unregister(array($this, ‘loadClass’));
}

/**
* Loads the given class or interface.
*
* @param string $class The name of the class
* @return bool|null True if loaded, null otherwise
*/
public function loadClass($class)
{
if ($file = $this->findFile($class)) {
includeFile($file);

return true;
}
}

/**
* Finds the path to the file where the class is defined.
*
* @param string $class The name of the class
*
* @return string|false The path if found, false otherwise
*/
public function findFile($class)
{
// 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
if (isset($this->classMap[$class])) {
return $this->classMap[$class];
}
if ($this->classMapAuthoritative) {
return false;
}

$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;
}

private function findFileWithExtension($class, $ext)
{
// PSR-4 lookup
$logicalPathPsr4 = strtr($class, ‘\\’, DIRECTORY_SEPARATOR) . $ext;

$first = $class[0];
if (isset($this->prefixLengthsPsr4[$first])) {
foreach ($this->prefixLengthsPsr4[$first] as $prefix => $length) {
if (0 === strpos($class, $prefix)) {
foreach ($this->prefixDirsPsr4[$prefix] as $dir) {
if (file_exists($file = $dir . DIRECTORY_SEPARATOR . substr($logicalPathPsr4, $length))) {
return $file;
}
}
}
}
}

// PSR-4 fallback dirs
foreach ($this->fallbackDirsPsr4 as $dir) {
if (file_exists($file = $dir . DIRECTORY_SEPARATOR . $logicalPathPsr4)) {
return $file;
}
}

// PSR-0 lookup
if (false !== $pos = strrpos($class, ‘\\’)) {
// namespaced class name
$logicalPathPsr0 = substr($logicalPathPsr4, 0, $pos + 1)
. strtr(substr($logicalPathPsr4, $pos + 1), ‘_’, DIRECTORY_SEPARATOR);
} else {
// PEAR-like class name
$logicalPathPsr0 = strtr($class, ‘_’, DIRECTORY_SEPARATOR) . $ext;
}

if (isset($this->prefixesPsr0[$first])) {
foreach ($this->prefixesPsr0[$first] as $prefix => $dirs) {
if (0 === strpos($class, $prefix)) {
foreach ($dirs as $dir) {
if (file_exists($file = $dir . DIRECTORY_SEPARATOR . $logicalPathPsr0)) {
return $file;
}
}
}
}
}

// PSR-0 fallback dirs
foreach ($this->fallbackDirsPsr0 as $dir) {
if (file_exists($file = $dir . DIRECTORY_SEPARATOR . $logicalPathPsr0)) {
return $file;
}
}

// PSR-0 include paths.
if ($this->useIncludePath && $file = stream_resolve_include_path($logicalPathPsr0)) {
return $file;
}
}
}

/**
* Scope isolated include.
*
* Prevents access to $this/self from included files.
*/
function includeFile($file)
{
include $file;
}

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autoload-psr规范代码
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