The static non-static method is shared between instances

Question

I came across some unexpected behavior with static variables defined inside methods of objects that are shared between instances. This is probably a known behavior, but when I look at the PHP documentation, I cannot find instances of statically defined variables in object methods.

The following is a description of the behavior I encountered:

<?php

class Foo {
  public function dofoo() {
    static $i = 0;
    echo $i++ . '<br>';
  }
}

$f = new Foo;
$g = new Foo;

$f->dofoo(); // expected 0, got 0
$f->dofoo(); // expected 1, got 1
$f->dofoo(); // expected 2, got 2

$g->dofoo(); // expected 0, got 3
$g->dofoo(); // expected 1, got 4
$g->dofoo(); // expected 2, got 5

Now I expected it to $ibe static on one instance, but actually $ishared between instances. For my own guidance, can someone explain why this is so, and where is it documented at php.net?

Answer 1

.

, ,

.

<?php

class Foo
{
    protected $_count = 0;
    public function doFoo()
    {
        echo $this->_count++, '<br>';
    }
}

: , . . , :

. .

, script ( ), "" ( , ). , , "", , .

Answer 2

, PHP , "scope" .

, ( hobodave), "" " ", , ( ) , "scoped" ( $foo, $foo).

, PHP 5 ( "static" " " ), , PHP.

, , PHP - , . , , PHP-, " ", , , , .

Answer 3

, , .

, .

class Foo {
  private $i = 0;
  public function dofoo() {
    echo $this->i++ . '<br>';
  }
}

Answer 4

. PHP 4 (, , ). / PHP 5.

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- . , .

. , .

Answer 5

7 , .

, ?!? , , .

:

namespace Statics;

class Foo
{
    protected static $_count;

    public function Bar()
    {
        return self::$_count++;
    }

    public function __construct()
    {
        self::$_count = 0;
    }
}

:

require 'Foo.php';

use Statics\Foo;

$bar = new Foo();
echo $bar->bar().'<br>';
echo $bar->bar().'<br>';
echo $bar->bar().'<br>';

$barcode = new Foo();
echo $barcode->bar().'<br>';
echo $barcode->bar().'<br>';
echo $barcode->bar().'<br>';

0
1
2
0
1
2

0! , , .

, ​​, , !

:

namespace Statics;

class Foo
{
    //default value
    protected static $_count = 0;

    public function Bar()
    {
        return self::$_count++;
    }

    public function __construct()
    {
       //do something else
    }
}

:

require 'Foo.php';

use Statics\Foo;

$bar = new Foo();
echo $bar->bar().'<br>';
echo $bar->bar().'<br>';
echo $bar->bar().'<br>';

$barcode = new Foo();
echo $barcode->bar().'<br>';
echo $barcode->bar().'<br>';
echo $barcode->bar().'<br>';

0
1
2
3
4
5

, , , , .

Hope this helps, and not that the answers above are incorrect, but I felt it was important to understand the whole concept from this point of view.

Regards, from Portugal!