<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8"/>
</head>
<body>
<form action="" method="POST">
    <fieldset>
        <legend>PESEL DECODER</legend>
        <p>Pesel: <input name="pesel"></p>
        <p><input name="sub1" type="submit" value="Prześlij"></p>
    </fieldset>
</form>

</body>
</html>

<?php

if (isset($_POST['sub1'])) {

    if (isset($_POST['pesel'])) {

        if (is_numeric($_POST['pesel'])) {
            $sum = 0;
            $weights = [1, 3, 7, 9, 1, 3, 7, 9, 1, 3];

            for ($i = 0; $i < $_POST['pesel'] - 1; $i++) {
                $sum += substr($_POST['pesel'], $i, $i + 1) * $weights[$i];
                echo "test<br>";
            }
            echo "test2";
            $sum = $sum % 10;
            if ($sum == 10)
                $sum = 0;
            if ($sum == $_POST['pesel'][10])
                $iscorrect = true;
            else
                $iscorrect = false;

            $year = substr($_POST['pesel'], 0, 2);
            $month = substr($_POST['pesel'], 2, 4);
            $day = substr($_POST['pesel'], 4, 6);
            if ($month >= 80) {
                $year += 1800;
                $month -= 80;
            } elseif ($month >= 60) {
                $year += 2200;
                $month -= 60;
            } elseif ($month >= 40) {
                $year += 2100;
                $month -= 40;
            } elseif ($month >= 20) {
                $year += 2000;
                $month -= 20;
            } else {
                $year += 1900;
            }

            if (substr($_POST['pesel'], 9, 10) % 2 == 1) {
                $sex = "mężczyzna";
            } else {
                $sex = "kobieta";
            }

            echo "Twoja data urodzenia to $day, $month $year<br>";
            echo "Płeć: $sex";
            echo $iscorrect;

        }

    } else {
        echo "Błędne dane, pesel powinien zawierać same liczby<br>";
    }
}


?>