Convert numbers to text (22 -> twenty-two) (FR) (PHP)

function numberToText($number) {

    $hyphen      = '-';
    $conjunction = ' ';
    $separator   = ' ';
    $negative    = 'moins ';
    $decimal     = ', ';
    $dictionary  = array(
        0                   => 'zéro',
        1                   => 'un',
        2                   => 'deux',
        3                   => 'trois',
        4                   => 'quatre',
        5                   => 'cinq',
        6                   => 'six',
        7                   => 'sept',
        8                   => 'huit',
        9                   => 'neuf',
        10                  => 'dix',
        11                  => 'onze',
        12                  => 'douze',
        13                  => 'treize',
        14                  => 'quatorze',
        15                  => 'quinze',
        16                  => 'seize',
        17                  => 'dix-sept',
        18                  => 'dix-huit',
        19                  => 'dix-neuf',
        20                  => 'vingt',
        30                  => 'trente',
        40                  => 'quarante',
        50                  => 'cinquante',
        60                  => 'soixante',
        70                  => 'soixante-dix',
        80                  => 'quatre-vingt',
        90                  => 'quatre-vingt-dix',
        100                 => 'cent',
        1000                => 'mille',
        1000000             => 'million',
        1000000000          => 'milliard',
        1000000000000       => 'trillion',
        1000000000000000    => 'quadrillion',
        1000000000000000000 => 'quintillion'
    );

    if (!is_numeric($number)) {
        return false;
    }

    if (($number >= 0 && (int) $number < 0) || (int) $number < 0 - PHP_INT_MAX) {
        // overflow
        trigger_error(
            'numberToText n'accepte que les nombres compris entre&nbsp;-' . PHP_INT_MAX . ' et&nbsp;' . PHP_INT_MAX,
            E_USER_WARNING
        );
        return false;
    }

    if ($number < 0) {
        return $negative . numberToText(abs($number));
    }

    $string = $fraction = null;

    if (strpos($number, '.') !== false) {
        list($number, $fraction) = explode('.', $number);
    }

    switch (true) {
        case $number < 21:
            $string = $dictionary[$number];
            break;
        case $number < 100:
            $tens   = ((int) ($number / 10)) * 10;
            $units  = $number % 10;
            $string = $dictionary[$tens];
            if ($units) {
                $string .= $hyphen . $dictionary[$units];
            }
            break;
        case $number < 1000:
            $hundreds  = $number / 100;
            $remainder = $number % 100;
            $string = $dictionary[$hundreds] . ' ' . $dictionary[100];
            if ($remainder) {
                $string .= $conjunction . numberToText($remainder);
            }
            break;
        default:
            $baseUnit = pow(1000, floor(log($number, 1000)));
            $numBaseUnits = (int) ($number / $baseUnit);
            $remainder = $number % $baseUnit;
            $string = numberToText($numBaseUnits) . ' ' . $dictionary[$baseUnit];
            if ($remainder) {
                $string .= $remainder < 100 ? $conjunction : $separator;
                $string .= numberToText($remainder);
            }
            break;
    }

    if (null !== $fraction && is_numeric($fraction)) {
        $string .= $decimal;
        $words = array();
        foreach (str_split((string) $fraction) as $number) {
            $words[] = $dictionary[$number];
        }
        $string .= implode(' ', $words);
    }

    return $string;
}