<?php
function convert_number_to_words($number) {

    $hyphen      = '-';
    $conjunction = ' and ';
    $separator   = ', ';
    $negative    = 'negative ';
    $decimal     = ' point ';
    $dictionary  = array(
        0                   =>'zero',
        1                   =>'one',
        2                   =>'two',
        3                   =>'three',
        4                   =>'four',
        5                   =>'five',
        6                   =>'six',
        7                   =>'seven',
        8                   =>'eight',
        9                   =>'nine',
        10                  =>'ten',
        11                  =>'eleven',
        12                  =>'twelve',
        13                  =>'thirteen',
        14                  =>'fourteen',
        15                  =>'fifteen',
        16                  =>'sixteen',
        17                  =>'seventeen',
        18                  =>'eighteen',
        19                  =>'nineteen',
        20                  =>'twenty',
        30                  =>'thirty',
        40                  =>'fourty',
        50                  =>'fifty',
        60                  =>'sixty',
        70                  =>'seventy',
        80                  =>'eighty',
        90                  =>'ninety',
        100                 =>'hundred',
        1000                =>'thousand',
        1000000             =>'million',
        1000000000          =>'billion',
        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(
'convert_number_to_words only accepts numbers between -' . PHP_INT_MAX . ' and ' . PHP_INT_MAX,
            E_USER_WARNING
        );
        return false;
    }

    if ($number < 0) {
        return $negative . convert_number_to_words(abs($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 .= $conjunction . convert_number_to_words($remainder);
            }
            break;
        default:
            $baseUnit = pow(1000, floor(log($number, 1000)));
            $numBaseUnits = (int) ($number / $baseUnit);
            $remainder = $number % $baseUnit;
            $string = convert_number_to_words($numBaseUnits) . '' . $dictionary[$baseUnit];
            if ($remainder) {
                $string .= $remainder < 100 ? $conjunction : $separator;
                $string .= convert_number_to_words($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;
}
?>