Y2S2 - Multiple Letter Submissions (data.php)

<?php
if (isset($_POST["Submit"]))
{
    if (!file_exists("letters.txt"))
    {
        $letters = fopen("letters.txt", "w+");
            fwrite($letters,
            "Уважаеми (а), " . $_POST["firstName_Receiver"] . " " . $_POST["lastName_Receiver"] . "<br />" . "\n" .
            $_POST["firstContext"] . "<br />" . "\n" .
            $_POST["secondContext"] . "<br />" . "\n" .
            $_POST["Afterword"] . ", " . $_POST["firstName_Sender"] . " " . $_POST["lastName_Sender"] . "!" . "\n" . "\n"
        );
    }
    else
    {
        $letters = fopen("letters.txt", "a+");
        fwrite($letters,
            "<hr />" . "Уважаеми (а), " . $_POST["firstName_Receiver"] . " " . $_POST["lastName_Receiver"] . "<br />" . "\n" .
            $_POST["firstContext"] . "<br />" . "\n" .
            $_POST["secondContext"] . "<br />" . "\n" .
            $_POST["Afterword"] . ", " . $_POST["firstName_Sender"] . " " . $_POST["lastName_Sender"] . "!" . "\n" . "\n"
        );
    }
    fclose($letters);
    echo file_get_contents("letters.txt");
}