eight / solution 8.3

<?php

function numbersToWords(string $t)
{
    return preg_replace_callback("/[\$]?-?\d+([,\s]?\d{3,})*/", "numberToWords", $t);
}

function numberToWords(array $n)
{
    $n = $n[0];
    // check for dollar amount
    $dollars = str_contains($n, "$");
    $n = str_replace("$", "", $n);
    // no need to process anything else if it's just 0
    if ($n == "0") {
        return "zero";
    }
    $n = str_replace([",", " "], "", $n) + 0;
    // keep track of whether it's a negative number
    $n < 0 ? ($n *= -1) && ($negative = true) : ($negative = false);
    $n = $n . "";
    $a = [];
    // break number into three-digit blocks for processing
    for ($i = 3; $i >= 0; $i--) {
        $a[$i] = substr($n, -3);
        $n = substr($n, 0, -3);
    }
    foreach ($a as &$i) {
        strlen($i) && ($i = numberBlockToWords($i));
    }
    $build = $negative ? "negative " : "";
    strlen($a[0]) && ($build .= " " . $a[0] . " billion ");
    strlen($a[1]) && ($build .= " " . $a[1] . " million ");
    strlen($a[2]) && ($build .= " " . $a[2] . " thousand ");
    strlen($a[3]) && ($build .= " " . $a[3] . " ");
    if ($dollars) {
        // this might look wrong in context but it's a good general application
        $build = trim($build) == "one" ? $build . " dollar " : $build . " dollars ";
    }
    return trim(preg_replace("/\s+/", " ", $build));
}

function numberBlockToWords(string $n)
{
    $a = [];
    for ($i = 2; $i >= 0; $i--) {
        $a[$i] = substr($n, -1);
        strlen($a[$i]) && ($a[$i] += 0);
        $n = substr($n, 0, -1);
    }
    $build = "";
    is_int($a[0]) && $a[0] > 0 && ($build .= " " . numberOnesToWords($a[0]) . " hundred ");
    is_int($a[1]) && $a[1] >= 2 && ($build .= " " . numberTensToWords($a[1]) . " ");
    is_int($a[1]) && $a[1] == 1 && ($a[2] += 10);
    is_int($a[2]) && $a[2] > 0 && ($build .= " " . numberOnesToWords($a[2]) . " ");
    return trim($build);
}

function numberOnesToWords(int $n)
{
    switch ($n) {
        case 1:
            return "one";
        case 2:
            return "two";
        case 3:
            return "three";
        case 4:
            return "four";
        case 5:
            return "five";
        case 6:
            return "six";
        case 7:
            return "seven";
        case 8:
            return "eight";
        case 9:
            return "nine";
        case 10:
            return "ten";
        case 11:
            return "eleven";
        case 12:
            return "twelve";
        case 13:
            return "thirteen";
        case 14:
            return "fourteen";
        case 15:
            return "fifteen";
        case 16:
            return "sixteen";
        case 17:
            return "seventeen";
        case 18:
            return "eighteen";
        case 19:
            return "nineteen";
    }
}
function numberTensToWords(int $n)
{
    switch ($n) {
        case 2:
            return "twenty";
        case 3:
            return "thirty";
        case 4:
            return "forty";
        case 5:
            return "fifty";
        case 6:
            return "sixty";
        case 7:
            return "seventy";
        case 8:
            return "eighty";
        case 9:
            return "ninety";
    }
}

$inputText = "is 100,987,000,423 a large number or no more significant than 42?";
$outputText = numbersToWords($inputText);
print_r($outputText . "\n\n");