PHP - Problema sentencia dentro de variable

$link='cursopresen.php?course_id=$encrypted_course_id';

while ($row = mysqli_fetch_assoc($result)) {

    //            echo json_encode($row);

    if ($row["status"]=="available")

        $courseId = $row["id"];

        //excryption of id

        $ciphering = "AES-128-CTR";

        $iv_length = openssl_cipher_iv_length($ciphering);

        $options = 0;

        $encryption_iv = '1234567891011121';

        $encryption_key = "@#!";

        $encrypted_course_id = openssl_encrypt($courseId, $ciphering,

                    $encryption_key, $options, $encryption_iv);

        $link='cursopresen.php?course_id=$encrypted_course_id';

    else

        $link="#";

    ?>

$link='cursopresen.php?course_id=$encrypted_course_id';