PHP Autoloading in Namespaces

问题

I have had a slight problem with autoloading in my namespace. As shown on the PHP manual here: http://us.php.net/manual/en/language.namespaces.rules.php you should be able to autoload namespace functions with a full qualified name e.g. \glue\common\is_email().

Thing is I have a function spl_autoload_register(array($import, "load")); within the initial namespace but whenever I try and call \glue\common\is_email() from the initial namespace it will not pass that autoload function but when using new is_email() (in the context of a class) it will. I don't get it the manual says I can autoload from fully qualified names but I can't :.

Here's my code:

namespace glue;

require_once 'import.php';

use glue\import as import;
use glue\core\router as router;

$import = new import();

spl_autoload_register(array($import, "load"));

/** Works and echos glue\router **/
$router = new router();

/** Don't do nothing **/
$cheese = \glue\common\is_email($email);

I also tried this code as well:

namespace glue;

require_once 'import.php';

use glue\import as import;
use glue\core\router as router;
use glue\common;

$import = new import();

spl_autoload_register(array($import, "load"));

/** Works and echos glue\router **/
$router = new router();

/** Don't do nothing **/
$cheese = common\is_email($email);

and finally this code:

namespace glue;

require_once 'import.php';

use glue\import as import;
use glue\core\router as router;
use glue\common\is_email as F;

$import = new import();

spl_autoload_register(array($import, "load"));

/** Works and echos glue\router **/
$router = new router();

/** Don't do nothing **/
$cheese = F($email);

回答1:

Here's the only right answer.

Every namespace needs its own spl_autoload_register() function.

also, spl_autoload_register() syntax changed in 5.3:

spl_autoload_register(__NAMESPACE__ . "\\className::functionName"));

The following should work:

namespace glue;

require_once 'import.php';

use glue\import as import;
use glue\core\router as router;

$import = new import();

spl_autoload_register(__NAMESPACE__ . "\\$import::load"));

/** Works and echos glue\router **/
$router = new router();

/** Don't do nothing **/
$cheese = \glue\common\is_email($email);

Here is some live code that Just works!

in ../WebPageConsolidator.inc.php:

class WebPageConsolidator
{
    public function __construct() { echo "PHP 5.2 constructor.\n"; }
}

in test.php:

<?php

namespace WebPage;

class MyAutoloader
{
    public static function load($className)
    {
        require '../' . __NAMESPACE__ . $className . '.inc.php';
    }
}

spl_autoload_register(__NAMESPACE__ . "\\MyAutoloader::load");

class Consolidator extends \WebpageConsolidator
{
    public function __construct()
    {
        echo "PHP 5.3 constructor.\n";

        parent::__construct();
    }
}

// Output: 
// PHP 5.3 constructor.
// PHP 5.2 constructor.

So I know it works.

回答2:

Use Composer to autoload your PHP Classes.

Check out how to do it in my recent blog post: https://enchanterio.github.io/enterprise-level-php/2017/12/25/the-magic-behind-autoloading-php-files-using-composer.html

回答3:

The misconception in the question of the OP is probably that functions/methods would be subject to autoloading – which they are not. Autoloading is only triggered by referencing classes.

This being said there still remains the question about autoloading classes in namespaces:

As of 2017 the current PHP-FIG standard for autoloading is PSR-4 which provides the following autoloader code for namespaced classes:

<?php
/**
 * An example of a project-specific implementation.
 *
 * After registering this autoload function with SPL, the following line
 * would cause the function to attempt to load the \Foo\Bar\Baz\Qux class
 * from /path/to/project/src/Baz/Qux.php:
 *
 *      new \Foo\Bar\Baz\Qux;
 *
 * @param string $class The fully-qualified class name.
 * @return void
 */
spl_autoload_register(function ($class) {

    // project-specific namespace prefix
    $prefix = 'Foo\\Bar\\';

    // base directory for the namespace prefix
    $base_dir = __DIR__ . '/src/';

    // does the class use the namespace prefix?
    $len = strlen($prefix);
    if (strncmp($prefix, $class, $len) !== 0) {
        // no, move to the next registered autoloader
        return;
    }

    // get the relative class name
    $relative_class = substr($class, $len);

    // 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('\\', '/', $relative_class) . '.php';

    // if the file exists, require it
    if (file_exists($file)) {
        require $file;
    }
});

The full spec text can be found at PSR-4: Autoloader.

The code example above (and another one to autoload from multiple namespaces) can be found at Example Implementations of PSR-4 (or GitHub: fig-standards/accepted/PSR-4-autoloader-examples.md).

来源：https://stackoverflow.com/questions/3642282/php-autoloading-in-namespaces