/src/ZfcDatagrid/Column/Formatter/FileSize.php

<?php
namespace ZfcDatagrid\Column\Formatter;

use ZfcDatagrid\Column\AbstractColumn;

class FileSize extends AbstractFormatter
{

    /**
     * We implement isApply here ourself, because it's always valid!
     *
     * @var unknown
     */
    protected $validRenderers = array();

    protected static $prefixes = array(
        '',
        'K',
        'M',
        'G',
        'T',
        'P',
        'E',
        'Z',
        'Y'
    );

    public function isApply()
    {
        return true;
    }

    /**
     * The value should be in bytes
     *
     * @see \ZfcDatagrid\Column\Formatter\AbstractFormatter::getFormattedValue()
     */
    public function getFormattedValue(AbstractColumn $column)
    {
        $row = $this->getRowData();
        $value = $row[$column->getUniqueId()];

        if ($value == '') {
            return $value;
        }

        $index = 0;
        while ($value >= 1024 && $index < count(self::$prefixes)) {
            $value = $value / 1024;
            $index ++;
        }

        return sprintf('%1.2f %sB', $value, self::$prefixes[$index]);
    }
}