JavaScript doesn't run after PHP header call

I'm trying to redirect using PHP header/even a JavaScript work around call inside php to my clients.php webpage.

The problem is that PHP header/the work around loads the webpage flawlessly but the Javascript still isn't ran.

Additional notes is that after the header or even Javascript redirect to the page, trying to refresh the page won't have the Javascript load. Only switching between a webpage and coming back to clients.php does the Javascript actually run.

I have also tried this: JavaScript not loading after PHP header() redirect

but to no avail.

Here are parts of my code segmented, just because its quite lengthy.

clients.php

<!-- Bootstrap core JavaScript-->
<script src="vendor/bootstrap/js/bootstrap.bundle.min.js"></script>
<!-- Core plugin JavaScript-->
<script src="vendor/jquery-easing/jquery.easing.min.js"></script>
<!-- Page level plugin JavaScript-->
<script src="vendor/chart.js/Chart.min.js"></script>
<script src="vendor/datatables/jquery.dataTables.js"></script>
<script src="vendor/datatables/dataTables.bootstrap4.js"></script>
<!-- Custom scripts for all pages-->
<script src="js/sb-admin.min.js"></script>
<!-- Custom scripts for this page-->
<script src="js/sb-admin-datatables.min.js"></script>
<script src="js/sb-admin-charts.min.js"></script>

    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js" ty    pe="text/javascript"></script>
    <link href="../../css/toastr.css" rel="stylesheet"/>
    <script src="../../js/toastr.js"></script>
    <script type="text/javascript">
            var tmp = "<?php $tmp = $_SESSION['message_success']; echo "$tmp"; ?>";
            alert(tmp + " h");
            $( document ).ready(function() {
                    <?php
                        if($_SESSION['sysLogin'] == "success") {
                            $_SESSION['sysLogin'] = "";
                            $user = $_SESSION['user'];
                            echo "toastr.success('Welcome $user', 'User has logged in');";
                        }
                        if($_SESSION['message_success'] != "") {
                            $msg = $_SESSION['message_success'];
                            $_SESSION['message_success'] = "";
                            echo "toastr.success('$msg', 'Success!');";
                        }
                        if($_SESSION['message_error'] != "") {
                            $msg = $_SESSION['message_error'];
                            $_SESSION['message_error'] = "";
                            echo "toastr.error('$msg', 'Error!');";
                        }
                        if($_SESSION['message_warning'] != "") {
                            $msg = $_SESSION['message_warning'];
                            $_SESSION['message_warning'] = "";
                            echo "toastr.warning('$msg', 'Warning!');";
                        }
                     ?>
            });
    </script>
    </div>
    </body>

    </html>

script.php

  if($update_statement) {
      $_SESSION['message_success'] = "$_membername's Careplan has been successfully updated.";
      echo "<script type='text/javascript'>window.location.href = '../clients.php';</script>";
      //header("Location:". $redirect);
      //exit();
    }

Note that clients.php and script.php are not in the same file.

Per Riggs request

<?php
session_start();
$message="";
if(isset($_POST["login"])) {
    $redirect = NULL;
    if($_POST['redirect'] != '') {
        $redirect = $_POST['redirect'];
    }
    if(empty($_POST['username']) || empty($_POST['password'])) {
        $message = "Both fields must be filled out.";
        $_SESSION['sysLogin'] = "$message";
        header("location: ../login.php?redirect=" . urlencode($redirect));
    } else {

        require('server_connection.inc');
        $connection = connect_to_db(DB_SERVER, DB_UN, DB_PWD, DB_NAME);

        $user=mysqli_real_escape_string($connection, $_POST['username']);
        $pass=mysqli_real_escape_string($connection, $_POST['password']);
        $statement = "select * from Credentials where UserName='$user' AND Password='$pass';";
        $result = $connection->query($statement);

        if($result->num_rows == 1) {
            // lets determine the type of user that logged in
            // if not employee but CEO, Manager, ETC, its an Admin
            $employeeid = ($result->fetch_assoc())["EmployeeID"];
            $check = "select Employees.Position, Employees.Name, Employees.ID from Credentials, Employees where (Credentials.EmployeeID = Employees.ID) AND Employees.ID = '$employeeid';";
            $result_two = $connection->query($check);
            if($result->num_rows == 1) {
                $the_row = $result_two->fetch_assoc();
                if($the_row["Position"] == "Employee") {
                    $name = $the_row["Name"];
                    $the_id = $the_row['ID'];
                    $_SESSION['logon'] = true;
                    $_SESSION['user'] = "$name";
                    $_SESSION['type'] = "employee";
                    $_SESSION['sysLogin'] = "success";
                    $_SESSION['user_id'] = $the_id;
                    mysqli_close($conection);
                    if($redirect) {
                          header("Location:". $redirect);
                    } else {
                        header("location: ../index.php");
                    }
                    exit();
                } else if($the_row["Position"] == "CEO" || $the_row["Position"] == "Manager") {
                    $name = $the_row["Name"];
                    $the_id = $the_row['ID'];
                    $_SESSION['logon'] = true;
                    $_SESSION['user'] = "$name";
                    $_SESSION['type'] = "admin";
                    $_SESSION['sysLogin'] = "success";
                    $_SESSION['user_id'] = $the_id;
                    mysqli_close($conection);
                    if($redirect) {
                            header("Location:". $redirect);
                    } else {
                        header("location: ../index.php");
                    }
                    exit();
                }
            } else {
                $message = "Unable to Parse Employee. Please contact your sites Administrator.";
                $_SESSION['sysLogin'] = "$message";
                mysqli_close($conection);
                header("location: ../login.php?redirect=" . urlencode($redirect));
            }
        } else if($result->num_rows == 0){
            $message = "Incorrect username or password";
            $_SESSION['sysLogin'] = "$message";
            mysqli_close($conection);
            header("location: ../login.php?redirect=" . urlencode($redirect));
        } else {
            $message = "Database Login Error. Too many retrieved accounts. Please contact your sites Administrator.";
            $_SESSION['sysLogin'] = "$message";
            mysqli_close($conection);
            header("location: ../login.php?redirect=" . urlencode($redirect));
        }
    }
}

function write_to_log($message) {
    $file = fopen("logfile.txt", "w") or die("Unable to open file!");
    fwrite($file, "$message\n");
    fclose($file);
}

function connect_to_db($server, $username, $pwd, $dbname) {
    $conn = mysqli_connect($server, $username, $pwd);
    if(!$conn) {
            echo "" . mysqli_error($conn);
            exit;
    }
    $dbh = mysqli_select_db($conn, $dbname);
    if(!$dbh) {
        echo "" . mysqli_error($conn);
        exit;
    }
    return $conn;
}
?>

This script merely links session while also checking for the login validity of the user

The message passing does indeed work with headers to another file 'dashboard.php' but redirecting from script.php to dashboard.php doesn't yield the message, thus an implication still arises.