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命名空间

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PHP手册 - N: 命名空间

用户评论:

Anonymous (25-May-2011 07:06)

The keyword 'use' has two different applications, but the reserved word table links to here.

It can apply to namespace constucts:

file1:
<?php namespace foo;
  class Cat {
    static function says() {echo 'meoow';}  } ?>

file2:
<?php namespace bar;
  class Dog {
    static function says() {echo 'ruff';}  } ?>

file3:
<?php namespace animate;
  class Animal {
    static function breathes() {echo 'air';}  } ?>

file4:
<?php namespace fub;
  include 'file1.php';
  include 'file2.php';
  include 'file3.php';
  use foo as feline;
  use bar as canine;
  use animate;
  echo \feline\Cat::says(), "<br />\n";
  echo \canine\Dog::says(), "<br />\n";
  echo \animate\Animal::breathes(), "<br />\n";  ?>

Note that
felineCat::says()
should be
\feline\Cat::says()
(and similar for the others)
but this comment form deletes the backslash (why???)

The 'use' keyword also applies to closure constructs:

<?php function getTotal($products_costs, $tax)
    {
        $total = 0.00;
       
        $callback =
            function ($pricePerItem) use ($tax, &$total)
            {
               
                $total += $pricePerItem * ($tax + 1.0);
            };
       
        array_walk($products_costs, $callback);
        return round($total, 2);
    }
?>

netmosfera at gmail dot com (22-Apr-2011 07:09)

for example, if you use a lot of .php files (once per class) you need to know that require() a lot of files will slow down consistently the page load

so you can use namespaces + autoload to implement package-specific initialization handlers

i used this to put an entire package (lot of classes) in one php file

!!! please note you can't use this as-is but you need to adapt it to your project

the file __init.php is placed inside every namespace/folder you want to load
there you can startup your namespace, check for environment, debugging, or as i do, you can merge all the package in one php file and require it to load other classes too.

<?php

class Loader
{
    // here we store the already-initialized namespaces
    private static $loadedNamespaces = array();
 
    static function loadClass($className)
    {
        // we assume the class AAA\BBB\CCC is placed in /AAA/BBB/CCC.php
        $className = str_replace(array('/', '\\'), \DIRECTORY_SEPARATOR, $className);
      
        // we get the namespace parts
        $namespaces = explode(\DIRECTORY_SEPARATOR, $className);
        unset($namespaces[sizeof($namespaces)-1]); // the last item is the classname
      
        // now we loops over namespaces
        $current=""; foreach($namespaces as $namepart)
        {
            // we chain $namepart to parent namespace string
            $current.='\\' . $namepart;
            // skip if the namespace is already initialized
            if(in_array($current, self::$loadedNamespaces)) continue;
            // wow, we got a namespace to load, so:
            $fnload = $current . \DIRECTORY_SEPARATOR . "__init.php";
            if(file_exists($fnload)) require($fnload);
            // then we flag the namespace as already-loaded
            self::$loadedNamespaces[] = $current;
        }

        // we build the filename to require
        $load = $className . ".php";
        // check for file existence
        !file_exists($load) ?: require($load);
        // return true if class is loaded
        return class_exists($className, false);
    }
    static function register()
    {
        spl_autoload_register("Loader::loadClass");
    }
    static function unregister()
    {
        spl_autoload_unregister("Loader::loadClass");
    }
}

Loader::register();

?>