get data url in mysql php

Question

How do you make the cookies in getdata.php retrieve data from the results of index.php?

// index.php

  <?php
    require_once('db/connection.php');
    // Fetch data from the database
    $stmt = $conn->prepare("SELECT * FROM user WHERE username = :username");
    $stmt->bindParam(':username', $_GET['username']);
    $stmt->execute();

    // Fetch data as an associative array
    $result = $stmt->fetch();

    // Check if data exists
    if(!$result) {
      header("Location: /monki/login");
      exit; // Terminate script after redirect
    }
  ?>

// getdata.php

  <?php
    require_once('../db/connection.php');

    // Fetch data from the database
    $stmt = $conn->query("SELECT post.*, user.*
    FROM post
    INNER JOIN user ON post.user_id = user.user_id
    WHERE post.user_id = '$_COOKIE[user_id]'");
    $stmt->bindParam(':user_id', $user_id);
    $posts = $stmt->fetchAll(PDO::FETCH_ASSOC);

    // Return the data as JSON
    header('Content-Type: application/json');
    echo json_encode($posts);
  ?> 

Creating get url in angularjs from database