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The Countable interface

(PHP 5 >= 5.1.0)

简介

Classes implementing Countable can be used with the count() function.

接口摘要

Countable {
/* 方法 */
abstract public int count ( void )
}

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PHP手册 - N: The Countable interface

用户评论:

Anonymous (17-Jan-2011 02:10)

Note that arrays don't implement countable. Therefore you can't force a countable parameter for a function if you want it also to work with native arrays.

isaac dot z dot foster dot nada at spamporfav dot gmail dot com (08-Jun-2010 09:18)

I just want to point out that your class has to actually implement the Countable interface, not just define a count method, to be able to use count($object) and get the expected results. I.e. the first example below won't work as expected, the second will. (The normal arrow function accessor ($object->count()) will work fine, but that's not the kewl part :) )

<?php
//Example One, BAD :(

class CountMe
{

    protected $_myCount = 3;

    public function count()
    {
        return $this->_myCount;
    }

}

$countable = new CountMe();
echo count($countable); //result is "1", not as expected

//Example Two, GOOD :)

class CountMe implements Countable
{

    protected $_myCount = 3;

    public function count()
    {
        return $this->_myCount;
    }

}

$countable = new CountMe();
echo count($countable); //result is "3" as expected
?>