命名空间概述

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);
    }
?>

down

Anonymous ¶

8 years ago

Tested on PHP 7.0.5, Windows
The line "use animate;" equals the line "use animate as animate;"
but the "use other\animate;" equals "use other\animate as animate;"

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 other\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 other\animate;       //use other\animate as animate;
  echo feline\Cat::says(), "<br />\n";
  echo canine\Dog::says(), "<br />\n";
  echo \animate\Animal::breathes(), "<br />\n";  ?>

down

varuninorbit at yahoo dot co dot in ¶

8 years ago

here is a simple example to use namespace

<?php

namespace app\a{
    class one{
       public static function _1(){
        echo 'a one _1<br>';
       }
    }
}

namespace app\b{
    class one{
        public static function _2(){
            echo 'b one _2<br>';
        }
    }
}

namespace app{

    echo a\one::_1();
    echo b\one::_2();
    echo a\two::_1();
}

namespace app\a{
    class two{
       public static function _1(){
        echo 'a two _1<br>';
       }
    }
}

prints 
a one _1
b one _2
a two _1

down

davidkennedy85 at gmail dot com ¶

9 years ago

In addition to using namespaces and closures, the use keyword has another new meaning as of PHP 5.4 - using traits:

<?php
trait Hello {
    public function sayHello() {
        echo 'Hello ';
    }
}

trait World {
    public function sayWorld() {
        echo 'World';
    }
}

class MyHelloWorld {
    use Hello, World;
    public function sayExclamationMark() {
        echo '!';
    }
}

$o = new MyHelloWorld();
$o->sayHello();
$o->sayWorld();
$o->sayExclamationMark();
?>

More info here: http://php.net/manual/en/language.oop5.traits.php

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