Abbreviate large numbers (1000 -> 1K). Fast approach. PHP

get-abbreviated-number.php

<?php

/**
 * Convert long integer number into abbreviated string.
 * Fast approach without math functions usage.
 * Integers up to 999 Uncentillions (1 Un = 1e306) are supported.
 *
 * getAbbreviatedNumber('1024'); // '1.02K'
 * getAbbreviatedNumber('-123456', 3); // '-123.456K'
 * getAbbreviatedNumber('1000000'); // '1M'
 *
 * Incorrect calls:
 * getAbbreviatedNumber('1 000 000 '); // Unexpected behavior! Remove whitespaces first.
 * getAbbreviatedNumber(1024); // Unexpected behavior! Number must be as string.
 *
 * @param string $integerNum The integer number to abbreviation. MUST BE without whitespaces and any other separators.
 * @param int $decimals The number of decimal digits.
 * @param string $decimalSeparator
 * @return ?string Abbreviated number or NULL when the integer is greater than 1e308
 */
function getAbbreviatedNumber(string $integerNum, int $decimals = 2, string $decimalSeparator = '.'): ?string
{
    /* Comments for number '1204567' (1 204 567). It's '1.2M'. */

    $minusSign = '';
    if ($integerNum[0] === '-') {
        $minusSign = '-';
        $integerNum = ltrim($integerNum, '-');
    }

    $numLen = strlen($integerNum); /* 7 */

    if ($numLen <= 3) {
        // Trap for numbers <= 999
        return $minusSign . $integerNum;
    }

    /**
     * @var array [
     *  'K' => 6,
     *  'M' => 9,
     *  'B' => 12,
     *  // and so on...
     * ]
     */
    static $rules = [];

    if ($rules === []) {
        $abbreviations = [
            # Million (up to 1e30)
            'K', // Thousand (Kilo) 1000 (10^3)
            'M', // Million (10^6)
            'B', // Billion (10^9)
            'T', // Trillion (10^12)
            'Qa', 'Qi', 'Sx', 'Sp', 'Oc', 'No',
            # Decillion (1e33 - 1e60)
            'Dc', 'Ud', 'Dd', 'Td', 'Qad', 'Qid', 'Sxd', 'Spd', 'Ocd', 'Nod',
            # Vigintillion (1e63 - 1e90)
            'Vg', 'Uvg', 'Dvg', 'Tvg', 'Qavg', 'Qivg', 'Sxvg', 'Spvg', 'Ocvg', 'Novg',
            # Trigintillion (1e93 - 1e120)
            'Tg', 'Utg', 'Dtg', 'Ttg', 'Qatg', 'Qitg', 'Sxtg', 'Sptg', 'Octg', 'Notg',
            # Quadragintillion (1e123 - 1e150)
            'Qag', 'Uqag', 'Dqag', 'Tqag', 'Qaqag', 'Qiqag', 'Sxqag', 'Spqag', 'Ocqag', 'Noqag',
            # Quinquagintillion (1e153 - 1e180)
            'Qig', 'UQig', 'DQig', 'TQig', 'QaQig', 'QiQig', 'SxQig', 'SpQig', 'OcQig', 'NoQig',
            # Sexagintillion (1e183 - 1e210)
            'Sxg', 'USxg', 'DSxg', 'TSxg', 'QaSxg', 'QiSxg', 'SxSxg', 'SpSxg', 'OcSxg', 'NoSxg',
            # Septuagintillion (1e213 - 1e240)
            'Spg', 'USpg', 'DSpg', 'TSpg', 'QaSpg', 'QiSpg', 'SxSpg', 'SpSpg', 'OcSpg', 'NoSpg',
            # Octogintillion (1e243 - 1e270)
            'Ocg', 'UOcg', 'DOcg', 'TOcg', 'QaOcg', 'QiOcg', 'SxOcg', 'SpOcg', 'OcOcg', 'NoOcg',
            # Nonagintillion (1e273 - 1e300)
            'Nog', 'UNog', 'DNog', 'TNog', 'QaNog', 'QiNog', 'SxNog', 'SpNog', 'OcNog', 'NoNog',
            # Centillion (1e303 - 1e306)
            'C', 'Uc',
            // Can be continued...
        ];

        $totalWidth = 3;
        foreach ($abbreviations as $abbreviation) {
            $totalWidth += 3;
            if (isset($rules[$abbreviation])) {
                throw new \RuntimeException("Rules: abbreviation '$abbreviation' is duplicated!");
            }
            $rules[$abbreviation] = $totalWidth;
        }
    }

    $abbreviation = null;
    $paddingTotalWidth = 0;

    foreach ($rules as $abbrev => $totalWidth) {
        if ($numLen <= $totalWidth) {
            $abbreviation = $abbrev;            /* M */
            $paddingTotalWidth = $totalWidth;   /* 9 */
            break;
        }
    }

    if ($abbreviation === null) {
        // It's astronomically, very big number
        return null;
    }

    $integerNum = str_pad($integerNum, $paddingTotalWidth, '0', STR_PAD_LEFT); /* '001204567' */

    $beforeSeparator = substr($integerNum, 0, 3);    /* '001' */
    $beforeSeparator = ltrim($beforeSeparator, '0'); /* '1' */

    $afterSeparator = substr($integerNum, 3, $decimals); /* '20' */
    $afterSeparator = rtrim($afterSeparator, '0');       /* '2' */

    if ($afterSeparator === '') {
        $decimalSeparator = '';
    }

    /* '' + '1' + '.' + '2' + 'M' */
    return $minusSign . $beforeSeparator . $decimalSeparator . $afterSeparator . $abbreviation;
}

/*
 * Testing
 */
echo '<pre>';

$nums = [
    '99'               => '99',
    '-99'              => '-99',
    '999'              => '999',
    '1000'             => '1K',
    '1900'             => '1.9K',
    '1090'             => '1.09K',
    '1009'             => '1K',
    '1999'             => '1.99K',
    '1249'             => '1.24K',
    '12499'            => '12.49K',
    '124999'           => '124.99K',
    '1234567'          => '1.23M',
    '1204567'          => '1.2M',
    '1249999'          => '1.24M',
    '12499999'         => '12.49M',
    '124999999'        => '124.99M',
    '1249999999'       => '1.24B',
    '1232973425'       => '1.23B',
    '12499999999'      => '12.49B',
    '124999999999'     => '124.99B',
    '1249999999999'    => '1.24T',
    '12499999999999'   => '12.49T',
    '124999999999999'  => '124.99T',
    '-124999999999999' => '-124.99T',
    '1249999999999999' => '1.24Qa',
    str_repeat('9', 309) => '999.99Uc',
    str_repeat('9', 310) => null,
];

var_dump('number => abbreviated number => is assert?');
foreach ($nums as $num => $abbreviatedNum) {
    $calculatedAbbreviatedNum = getAbbreviatedNumber($num);
    $assert = $calculatedAbbreviatedNum === $abbreviatedNum;
    var_dump("$num => $calculatedAbbreviatedNum => " . ($assert ? 'true' : 'FALSE'));
}

/*
 * Performance testing
 */
$start = microtime(true);

// 100 000 iteration of 999 uncentillions converting

$n = str_repeat('9', 309);
for ($i = 0; $i <= 100000; $i++) {
    getAbbreviatedNumber($n);
}

$finish = round(microtime(true) - $start, 2);
var_dump($finish . ' sec'); // 0.26 sec on PHP 7.4

echo '</pre>';