PHP - Filter iterator

php_filter_iterator.php

<?php 
/**
 * Class ServerList
 */
class ServersList extends RecursiveArrayIterator
{

}

/**
 * Class ServerListManager
 */
class ServersListFilter extends FilterIterator
{

    protected $filterKey = null, $filterValue = null;

    /**
     * Wrapper to accept();
     * @param $key
     * @param $value
     * @return bool
     */
    public function filterBy($key, $value)
    {

        $this->filterKey = $key;
        $this->filterValue = $value;

        return $this->accept();
    }

    /**
     * Check whether the current element of the iterator is acceptable
     * @link http://php.net/manual/en/filteriterator.accept.php
     * @return bool true if the current element is acceptable, otherwise false.
     * @since 5.1.0
     */
    public function accept()
    {

        if (!$this->filterKey || !$this->filterValue) {
            throw new RuntimeException("Filter was not set! ".__METHOD__);
        }
        $item = $this->getInnerIterator()->current();
        if (isset($item[$this->filterKey])) {
            return ($this->filterValue === $item[$this->filterKey]);
        }

        return null;
    }
}


$serverList = new ServersList(
    array(
        'server_01' => array(
            'location' => 'EU',
            'availability' => true,
            'name' => 'chopin01',
            'services' => array(
                'http' => 80,
                'ssh' => 22,
            ),
        ),
        'server_02' => array(
            'location' => 'US',
            'availability' => false,
            'name' => 'mozart01',
            'services' => array(
                'http' => 80,
                'ssh' => 22,
            ),
        ),
        'server_03' => array(
            'location' => 'EU',
            'availability' => true,
            'name' => 'chopin02',
            'services' => array(
                'http' => 8080,
                'ssh' => 22,
            ),
        ),
    )
);

$iterator = new ServersListFilter($serverList);
$iterator->accept();
$iterator->filterBy('availability', true);
$output = array();
foreach ($iterator as $key => $value) {
    print_r($value);
}
// Output:
/*
[
    {
        location: "EU",
        availability: "1",
        name: "chopin01",
        services:
        {
            http: "80",
            ssh: "22"
        }
},
{
        location: "EU",
        availability: "1",
        name: "chopin02",
        services:
        {
            http: "8080",
            ssh: "22"
        }
    }
]
*/