<link rel="stylesheet" href="examplestyle.css">

<span id="site_description"></span>

let htmlcode = ["#efefef", "#181B39", "#262a2e", "#192734", "#1c483b", "#bf7800", "#83094f"].map(elm => `<span class='color_code' style='color:${elm}' data-color-code='${elm}'>■</span>`).join("\n");

const basecolor = "#262a2e";
let cookiefn = function (CodeColor) {
    let r = document.cookie.split(';');
    return r.length ? ((r) => {
        let changecolor = "";
        for (let ii = 0; ii < r.length; ii++) {
            let content = r[ii].split('=');
            for (let i = 0; i < content.length; i++) {
                if (content[i].replaceAll(" ", "") === "bgcolor_code") {
                    changecolor = content[i + 1];
                }
            }
        }
        return changecolor?changecolor:CodeColor;
    })(r) : CodeColor;
};

let old_color = cookiefn(basecolor);
document.getElementById("site_description").insertAdjacentHTML("afterend", htmlcode);
[...document.querySelectorAll(".color_code")].forEach(elm => {
    elm.addEventListener("click", function (e) {
        color_set(elm.getAttribute("data-color-code"));
    });
});

color_set(old_color);

function color_set(color) {
    for (let ii = 0; ii < document.styleSheets.length; ii++) {
        if (String(document.styleSheets[ii].href).match(/mag_tcd036-child\/style\.css\?ver=/)) {
            for (let i = 0; i < document.styleSheets[ii].cssRules.length; i++) {
                let element_css_code = document.styleSheets[ii].cssRules[i];
                try {
                    element_css_code.style.backgroundColor = color;
                    if (color === "#efefef") {
                        element_css_code.style.color = "#000000";
                        
                    } else {
                        element_css_code.style.color = "#FFFFFF";
                    }
//いらないかも領域🤔👇
                    document.querySelectorAll("#wp-calendar > tbody > tr > td > a").forEach(elm=>{
                        elm.style.backgroundColor = "#909091";
                    });
                    document.getElementById("searchsubmit").style.backgroundColor = "#000";
                    document.querySelector("#s").style.backgroundColor = "#909091";
                    [...document.querySelectorAll("code")].forEach(elm=>{
                        [...elm.querySelectorAll("span")].forEach(childen_elm=>{
                            childen_elm.style.backgroundColor = "#565656";
                        });
                    });
//いらないかも領域🤔👆                    
                } catch (error) {
                }
            }

            document.cookie = "bgcolor_code=" + color;
        }
    }
}

<?php
header('Access-Control-Allow-Origin: *');
date_default_timezone_set('Asia/Tokyo');
$birth_date = (string)$_POST["birth_date"];
$max_age = (int)$_POST["point_age"];

/**
 * @param string $birth_date
 * @return string|false
 */
function check1($birth_date = ""): bool
{
    $flg = false;
    $str_date = explode("/", $birth_date);
    if (count($str_date) === 3) {
        $flg = true;
        if (!((int)$str_date[0] >= 1000)) {
            $flg = false;
        }
        if(((int)$str_date[0] > (int)date("Y"))){
            $flg = false;
        }
        if (!((int)$str_date[1] >= 1 && (int)$str_date[1] <= 12)) {
            $flg = false;
        }
        if ($flg) {
            if ((int)$str_date[1] === 2) {
                if (!((int)$str_date[2] >= 1 && (int)$str_date[2] <= 28)) {
                    $flg = false;
                }
                if ((int)$str_date[0] % 4 === 0) {
                    $flg = true;
                    if (!((int)$str_date[2] >= 1 && (int)$str_date[2] <= 29)) {
                        $flg = false;
                    }
                    if ((int)$str_date[0] % 100 === 0) {
                        $flg = true;
                        if (!((int)$str_date[2] >= 1 && (int)$str_date[2] <= 28)) {
                            $flg = false;
                        }
                        if ((int)$str_date[0] % 400 === 0) {
                            $flg = true;
                            if (!((int)$str_date[2] >= 1 && (int)$str_date[2] <= 29)) {
                                $flg = false;
                            }
                        }
                    }
                }
            } else {
                $last_day = [4, 6, 9, 11];
                if (array_search((int)$str_date[1], $last_day, false)!== false) {
                    if (!((int)$str_date[2] >= 1 && (int)$str_date[2] <= 30)) {
                        $flg = false;
                    }
                } else {
                    if (!((int)$str_date[2] >= 1 && (int)$str_date[2] <= 31)) {
                        $flg = false;
                    }
                }
            }
        }
    }
    return $flg;
}

/**
 * @param int $age
 * @return string|false
 */
function check2($age = 0): bool
{
    $flg = true;
    if ($age < 0) {
        $flg = false;
    }
    return $flg;
}


/**
 * @param string $birth_date
 * @param string $maxage
 * @return string $reslut
 */
function sumup($birth_date, $maxage)
{
    $reslut = [];
    $birth_date_array = explode("/", $birth_date);
    $birth_date = sprintf("%04d%02d%02d", $birth_date_array[0], $birth_date_array[1], $birth_date_array[2]);
    $today = date('Ymd');
    $age = floor(($today - $birth_date) / 10000);
    $day1 = new DateTime("{$birth_date_array[0]}-{$birth_date_array[1]}-{$birth_date_array[2]}");
    $day2 = new DateTime();    
    $interval1 = $day1->diff($day2, true);
    $baseday =  (int)($interval1->format('%a'));
    if ((int)$maxage <= (int)$age) {
        $pointday = 0;
    } else {
        $maxage--;
        $day3 = new DateTime((date('Y') + ($maxage - $age)) . "-{$birth_date_array[1]}-{$birth_date_array[2]}");
        $interval2 = $day2->diff($day3, true);
        $pointday = (int)($interval2->format('%a'))+1;
    }


    $reslut = [
        [
            "result" => "success",
            "age"=>$age ."歳",
            "baseday" => $baseday . "日(生きてきた日数)",
            "pointday" => $pointday . "日(" .($maxage +1). "歳まであと)"
        ]
    ];
    return json_encode($reslut);
}

if (!check1($birth_date)) {
    print json_encode([
        [
            "result" => "error",
            "error" => "string is invalid1"
        ]
    ]);
} elseif (!check2($max_age)) {
    print json_encode([
        [
            "result" => "error",
            "error" => "string is invalid2"
        ]
    ]);
} else {
    print sumup($birth_date, $max_age);
}