I made a very basic polyfill for this function, you're welcome to use

<?php
if(!function_exists('ini_parse_quantity')) {
    /**
     * Very basic polyfill for ini_parse_quantity
     * @license MPL-2.0
     * @license CC-BY-3.0
     */
    function ini_parse_quantity($shorthand) {
        $regex = '/^(0?[xXbBoO]?)([0-9A-Fa-f]*)([kKmMgG]?)$/';
        preg_match($regex, $shorthand, $matches);
        if(empty($matches)) {
            trigger_error('Can\'t parse '.$shorthand.' :(', E_USER_WARNING);
            return 0;
        }
        [ $full, $binOctHex, $value, $unit ] = $matches;
        switch ($binOctHex) {
            case '0b':
            case '0B':
                $base = 2;
                break;
            case '0o':
            case '0O':
            case '0':
                $base = 8;
                break;
            case '0x':
            case '0X':
                $base = 16;
                break;
            default:
                $base = 10;
                break;
        }
        $value = intval($value, $base);

        switch ($unit) {
            case 'g':
            case 'G':
                $value *= 1024;
            case 'm':
            case 'M':
                $value *= 1024;
            case 'k':
            case 'K':
                $value *= 1024;
            default:
                break;
        }
        return $value;
    }
}