PHP Roman Numerals Code Kata solution. A collaborative effort of the people @ PHP User Group Rheinhessen, Jan '13.

Roman.php

<?php

/**
 * Converts Roman numbers to integers
 */
class Roman
{
    /**
     * @var array
     */
    protected $d = array(
        'I' => 1,
        'V' => 5,
        'X' => 10,
        'L' => 50,
        'C' => 100,
        'D' => 500,
        'M' => 1000,
    );
    
    /**
     * @param string $roman
     */
    public function toInt($roman)
    {
        $res = 0;
        $chars = str_split($roman);
        $length = count($chars);
        for ($i = 0; $i < $length; $i++) {
            if (isset($chars[$i+1]) && $this->d[$chars[$i+1]] > $this->d[$chars[$i]]) {
                $res -= $this->d[$chars[$i]];
            } else {
                $res += $this->d[$chars[$i]];
            }
        }
        return $res;
    }
}