Convert a numerical value to the readable string notated equivalent.

<?php

    /**
     * Formats a number with a level of precision (even if it had none).
     *
     * @param float $number
     * @param int $precision
     * @return float
     */
    function precision($number, $precision = 2)
    {
        return sprintf('.' . $precision . 'F', $number);
    }

    /**
     * Convert a numerical value to the readable string notated equivalent.
     *
     * @param int $size
     * @param int $precision
     * @return string
     */
    function bytesTo($size, $precision = 0)
    {
        $sizes = array(
            'YB',
            'ZB',
            'EB',
            'PB',
            'TB',
            'GB',
            'MB',
            'KB',
            'B'
        );

        $total = count($sizes);

        while ($total -- && $size >= 1024)
            {
                $size /= 1024;
            }

        return precision($size, $precision) . $sizes[$total];
    }