标签：php psr-0 psr-4 autoloading composer
在上一篇文章中，介绍了PSR-0和autoload相关的内容。继PSR-0这个PHP autoloading的规范之后，PHP-FIG又推出了PSR-4，称为改进的autoloading规范。
在PSR-0中，\Symfony\Core\Request会被转换成文件系统的/path/to/project/lib/vendor/Symfony/Core/Request.php这个路径。PSR-4与PSR-0在内容上相差也不大。
在此就不详谈两者的定义了。来看看两者在实际中的一些区别吧。由于Composer的流行，这里对Composer中这两种风格进行比较。
在Composer中，遵循PSR-0标准的典型目录结构是这样的：
vendor/
vendor_name/
package_name/
src/
Vendor_Name/
Package_Name/
ClassName.php # Vendor_Name\Package_Name\ClassName
tests/
Vendor_Name/
Package_Name/
ClassNameTest.php # Vendor_Name\Package_Name\ClassNameTest
可以看到目录结构有明显的重复而且层次很深。src/和test/目录又重新包含了Vendor和Package目录。
再来看看PSR-4的：
vendor/
vendor_name/
package_name/
src/
ClassName.php # Vendor_Name\Package_Name\ClassName
tests/
ClassNameTest.php # Vendor_Name\Package_Name\ClassNameTest可以看到目录结构更加简洁了。
在PSR-0中目录结构要与命名空间层层对应，无法插入一个单独的目录。而PSR-4可以。
对比PSR-0，除了PSR-4可以更简洁外，需要注意PSR-0中对下划线(_)是有特殊的处理的，下划线会转换成DIRECTORY_SEPARATOR，这是出于对PHP5.3以前版本兼容的考虑，而PSR-4中是没有这个处理的，这也是两者比较大的一个区别。
此外，PSR-4要求在autoloader中不允许抛出exceptions以及引发任何级别的errors，也不应该有返回值。这是因为可能注册了多个autoloaders，如果一个autoloader没有找到对应的class，应该交给下一个来处理，而不是去阻断这个通道。
PSR-4更简洁更灵活了，但这使得它相对更复杂了。例如通过完全符合PSR-0标准的class name，通常可以明确的知道这个class的路径，而PSR-4可能就不是这样了。
Given a foo-bar package of classes in the file system at the following paths ...
/path/to/packages/foo-bar/
src/
Baz.php # Foo\Bar\Baz
Qux/
Quux.php # Foo\Bar\Qux\Quux
tests/
BazTest.php # Foo\Bar\BazTest
Qux/
QuuxTest.php # Foo\Bar\Qux\QuuxTest
... add the path to the class files for the \Foo\Bar\ namespace prefix as follows:
<?php
// instantiate the loader
$loader = new \Example\Psr4AutoloaderClass;
// register the autoloader
$loader->register();
// register the base directories for the namespace prefix
$loader->addNamespace('Foo\Bar', '/path/to/packages/foo-bar/src');
$loader->addNamespace('Foo\Bar', '/path/to/packages/foo-bar/tests');
//此时一个namespace prefix对应到了多个"base directory"
//autoloader会去加载/path/to/packages/foo-bar/src/Qux/Quux.php
new \Foo\Bar\Qux\Quux;
//autoloader会去加载/path/to/packages/foo-bar/tests/Qux/QuuxTest.php
new \Foo\Bar\Qux\QuuxTest;
下面是如上PSR-4 autoloader的实现：
<?php
namespace Example;
class Psr4AutoloaderClass
{
/**
* An associative array where the key is a namespace prefix and the value
* is an array of base directories for classes in that namespace.
*
* @var array
*/
protected $prefixes = array();
/**
* Register loader with SPL autoloader stack.
*
* @return void
*/
public function register()
{
spl_autoload_register(array($this, 'loadClass'));
}
/**
* Adds a base directory for a namespace prefix.
*
* @param string $prefix The namespace prefix.
* @param string $base_dir A base directory for class files in the
* namespace.
* @param bool $prepend If true, prepend the base directory to the stack
* instead of appending it; this causes it to be searched first rather
* than last.
* @return void
*/
public function addNamespace($prefix, $base_dir, $prepend = false)
{
// normalize namespace prefix
$prefix = trim($prefix, '\\') . '\\';
// normalize the base directory with a trailing separator
$base_dir = rtrim($base_dir, '/') . DIRECTORY_SEPARATOR;
$base_dir = rtrim($base_dir, DIRECTORY_SEPARATOR) . '/';
// initialize the namespace prefix array
if (isset($this->prefixes[$prefix]) === false) {
$this->prefixes[$prefix] = array();
}
// retain the base directory for the namespace prefix
if ($prepend) {
array_unshift($this->prefixes[$prefix], $base_dir);
} else {
array_push($this->prefixes[$prefix], $base_dir);
}
}
/**
* Loads the class file for a given class name.
*
* @param string $class The fully-qualified class name.
* @return mixed The mapped file name on success, or boolean false on
* failure.
*/
public function loadClass($class)
{
// the current namespace prefix
$prefix = $class;
// work backwards through the namespace names of the fully-qualified
// class name to find a mapped file name
while (false !== $pos = strrpos($prefix, '\\')) {
// retain the trailing namespace separator in the prefix
$prefix = substr($class, 0, $pos + 1);
// the rest is the relative class name
$relative_class = substr($class, $pos + 1);
// try to load a mapped file for the prefix and relative class
$mapped_file = $this->loadMappedFile($prefix, $relative_class);
if ($mapped_file) {
return $mapped_file;
}
// remove the trailing namespace separator for the next iteration
// of strrpos()
$prefix = rtrim($prefix, '\\');
}
// never found a mapped file
return false;
}
/**
* Load the mapped file for a namespace prefix and relative class.
*
* @param string $prefix The namespace prefix.
* @param string $relative_class The relative class name.
* @return mixed Boolean false if no mapped file can be loaded, or the
* name of the mapped file that was loaded.
*/
protected function loadMappedFile($prefix, $relative_class)
{
// are there any base directories for this namespace prefix?
if (isset($this->prefixes[$prefix]) === false) {
return false;
}
// look through base directories for this namespace prefix
foreach ($this->prefixes[$prefix] as $base_dir) {
// replace the namespace prefix with the base directory,
// replace namespace separators with directory separators
// in the relative class name, append with .php
$file = $base_dir
. str_replace('\\', DIRECTORY_SEPARATOR, $relative_class)
. '.php';
$file = $base_dir
. str_replace('\\', '/', $relative_class)
. '.php';
// if the mapped file exists, require it
if ($this->requireFile($file)) {
// yes, we're done
return $file;
}
}
// never found it
return false;
}
/**
* If a file exists, require it from the file system.
*
* @param string $file The file to require.
* @return bool True if the file exists, false if not.
*/
protected function requireFile($file)
{
if (file_exists($file)) {
require $file;
return true;
}
return false;
}
}单元测试代码：
<?php
namespace Example\Tests;
class MockPsr4AutoloaderClass extends Psr4AutoloaderClass
{
protected $files = array();
public function setFiles(array $files)
{
$this->files = $files;
}
protected function requireFile($file)
{
return in_array($file, $this->files);
}
}
class Psr4AutoloaderClassTest extends \PHPUnit_Framework_TestCase
{
protected $loader;
protected function setUp()
{
$this->loader = new MockPsr4AutoloaderClass;
$this->loader->setFiles(array(
'/vendor/foo.bar/src/ClassName.php',
'/vendor/foo.bar/src/DoomClassName.php',
'/vendor/foo.bar/tests/ClassNameTest.php',
'/vendor/foo.bardoom/src/ClassName.php',
'/vendor/foo.bar.baz.dib/src/ClassName.php',
'/vendor/foo.bar.baz.dib.zim.gir/src/ClassName.php',
));
$this->loader->addNamespace(
'Foo\Bar',
'/vendor/foo.bar/src'
);
$this->loader->addNamespace(
'Foo\Bar',
'/vendor/foo.bar/tests'
);
$this->loader->addNamespace(
'Foo\BarDoom',
'/vendor/foo.bardoom/src'
);
$this->loader->addNamespace(
'Foo\Bar\Baz\Dib',
'/vendor/foo.bar.baz.dib/src'
);
$this->loader->addNamespace(
'Foo\Bar\Baz\Dib\Zim\Gir',
'/vendor/foo.bar.baz.dib.zim.gir/src'
);
}
public function testExistingFile()
{
$actual = $this->loader->loadClass('Foo\Bar\ClassName');
$expect = '/vendor/foo.bar/src/ClassName.php';
$this->assertSame($expect, $actual);
$actual = $this->loader->loadClass('Foo\Bar\ClassNameTest');
$expect = '/vendor/foo.bar/tests/ClassNameTest.php';
$this->assertSame($expect, $actual);
}
public function testMissingFile()
{
$actual = $this->loader->loadClass('No_Vendor\No_Package\NoClass');
$this->assertFalse($actual);
}
public function testDeepFile()
{
$actual = $this->loader->loadClass('Foo\Bar\Baz\Dib\Zim\Gir\ClassName');
$expect = '/vendor/foo.bar.baz.dib.zim.gir/src/ClassName.php';
$this->assertSame($expect, $actual);
}
public function testConfusion()
{
$actual = $this->loader->loadClass('Foo\Bar\DoomClassName');
$expect = '/vendor/foo.bar/src/DoomClassName.php';
$this->assertSame($expect, $actual);
$actual = $this->loader->loadClass('Foo\BarDoom\ClassName');
$expect = '/vendor/foo.bardoom/src/ClassName.php';
$this->assertSame($expect, $actual);
}
}完。
标签：php psr-0 psr-4 autoloading composer
原文地址：http://blog.csdn.net/sky_zhe/article/details/38615615
