Parsing crazy telephone numbers

numbers

<?php
function filter_number($number) {
    if (substr($number, 0, 2) == "00") {
        $number = "+". (string)(float)$number;
    }
    $l = strlen($number);
    $retval = array(0 => "");
    $idx = 0;
    for($n=0; $n<$l; $n++) {
        switch($number[$n]) {
        case " ":
        case ",":
        case "/":
            if (strlen($retval[$idx]) >= 7 && ($l-$n > 8)) {
                ++$idx;
                $retval[$idx] = "";
            }
            if (!isset($number[$n+1]) ) {
                break 2;
            }
            continue 2;
        case "+":
            if (strlen($retval[$idx]) == 0) {
                $retval[$idx] = "+";
            } elseif($l-$n > 8) {
                $idx++;
                $retval[$idx] = "";
            }  else {
            }

        default:
            if (is_numeric($number[$n])) {
                $retval[$idx] .= $number[$n];
            }
        }
    }
    if (!$retval[0]) {
        return false;
    }
    if (strlen(end($retval)) < 8) {
        array_pop($retval);
    }

    foreach($retval as &$number) {
        if ($number[0] == "0") {
            $number = substr($number, 1);
        }

        if ($number[0] == "+") {
            continue;
        }
        switch(substr($number, 0, 2)) {
        case '47':
        case '46':
            $number = "+" . $number;
            break;
        default:
            $number = "+46" . $number;
        }
    }
    return $retval;
}