gistfile1.php

<?php

/**
 * Reconstruct an array, for small task at: http://www.phpgangsta.de/kleine-aufgabe-ein-array-umbauen
 * Contribution by DracoBlue
 */

function compress($in)
{
    $in_length = count($in);
    $start = $last = $current = $in[0];
    $direction = 0;
    $out = array();

    $i = 1;

    while ($i < $in_length)
    {
        $last = $current;
        $current = $in[$i++];

        if ($last - 1 === $current && $direction >= 0)
        {
            $direction = 1;
            continue;
        }
        elseif ($last + 1 === $current && $direction <= 0)
        {
            $direction = -1;
            continue;
        }
        elseif ($start !== $last)
        {
            $out[] = $start . '-' . $last;
        }
        else
        {
            $out[] = $start;
        }

        $direction = 0;
        $start = $current;
    }
    $last = $current;

    if ($start !== $last)
    {
        $out[] = $start . '-' . $last;
    }
    else
    {
        $out[] = $start;
    }

    return $out;
}

function decompress($in)
{
    $out = array();

    foreach ($in as $current)
    {
        if (is_string($current))
        {
            list($start, $end) = explode('-', $current);
        
            foreach (range($start, $end) as $value)
            {
                $out[] = $value;
            }
        }
        else
        {
            $out[] = $current;
        }
    }

    return $out;

}