Untitled

<?php
    define('DEFAULT_YEAR', 1987, true);

    $current_year = date('Y');
    $result = '';

    /*
       0. if age is number
       1. Years to be lower from current
       2. if $age is in short format(`87)
       3. if it is <> from 100
       4.

       this is homework !!

     */

    if(isset($_GET['age']))
    {
        $result = $current_year - $_GET['age'];
    }

?>


<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8" />
    <title>Ex2.PHP1 Forms</title>
</head>
<body>
    <h2>Exercise 2 - Forms</h2>
    <?php echo $result; ?>

    <form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="GET">

        <input type="number" name="age" value="<?php echo (isset($_GET['age']) && is_numeric($_GET['age']) ? $_GET['age']: DEFAULT_YEAR );  ?>" />
        <br />
        <input type="submit" name="submit" value="Submit" />

    </form>

    <?php
        if(!empty($_GET))
        {

        }
        else
        {

        }
    ?>
</body>
</html>