Issue with AJAX Request Triggering Unrelated Method in PHP

I am trying to update the like/upvote button. For that I have created a menthod[Method named: likepost()] in my Controller named Posts. Here is the code for my method.

public function likepost() 
{
  if (IsloggedIn()) {
      // Check if the request is a POST request
      if ($_SERVER['REQUEST_METHOD'] == 'POST') {
          $post_id = $_POST['post_id'];
          $user_id = $_SESSION['user_id']; // Assuming the user is logged in and we are storing the user ID in session
  
          // Check if the user already liked this post
          if ($this->postModel->hasUserLikedPost($post_id, $user_id)) {
              // User has already liked the post, so we need to remove the like
              if ($this->postModel->removeLike($post_id, $user_id)) {
                  // Decrease the like count in the posts table
                  $this->postModel->decrementLikeCount($post_id);
                  echo json_encode(['status' => 'unliked', 'likes_count' => $this->postModel->getLikesCount($post_id)]);
              }
          } else {
              // User has not liked the post, so we add the like
              if ($this->postModel->addLike($post_id, $user_id)) {
                  // Increase the like count in the posts table
                  $this->postModel->incrementLikeCount($post_id);
                  echo json_encode(['status' => 'liked', 'likes_count' => $this->postModel->getLikesCount($post_id)]);
              }
          }
      } else {
          echo json_encode(['status' => 'error', 'message' => 'Invalid request']);
      }
  } else {
      echo json_encode(['status' => 'error', 'message' => 'User not logged in']);
  }
}

Following is the code for my Model:

        public function hasUserLikedPost($user_id, $post_id) {
          echo $this->db->query('SELECT * FROM post_likes WHERE user_id = :user_id AND post_id = :post_id');
          $this->db->bind(':user_id', $user_id);
          $this->db->bind(':post_id', $post_id);
          $row = $this->db->single();
          
          return $row ? true : false;
      }
      
      public function addLike($post_id, $user_id) {
        $this->db->query('INSERT INTO post_likes (post_id, user_id) VALUES (:post_id, :user_id)');
        $this->db->bind(':post_id', $post_id);
        $this->db->bind(':user_id', $user_id);
        return $this->db->execute();
      }
    
      public function removeLike($post_id, $user_id) {
        $this->db->query('DELETE FROM post_likes WHERE post_id = :post_id AND user_id = :user_id');
        $this->db->bind(':post_id', $post_id);
        $this->db->bind(':user_id', $user_id);
        return $this->db->execute();
      }
    
      public function incrementLikeCount($post_id) {
        $this->db->query('UPDATE posts SET likes_count = likes_count + 1 WHERE id = :post_id');
        $this->db->bind(':post_id', $post_id);
        return $this->db->execute();
      }
    
      public function decrementLikeCount($post_id) {
        $this->db->query('UPDATE posts SET likes_count = likes_count - 1 WHERE id = :post_id');
        $this->db->bind(':post_id', $post_id);
        return $this->db->execute();
      }
    
    public function getLikesCount($post_id) {
      $this->db->query('SELECT likes_count FROM posts WHERE id = :post_id');
      $this->db->bind(':post_id', $post_id);
      return $this->db->single()->likes_count;
    }

Here is my view code:

    <button class="btn btn-success" id="upvote" data-post-id='<?php echo $data['post']->id; ?>'>
    <i class="fa fa-thumbs-up"></i> Upvote <span id="display"><?php echo $data['post']->likes_count; ?></span>
  </button>

Following is my AJAX query written in my main.js

        document.addEventListener("DOMContentLoaded", function () {
      let btn = document.getElementById("upvote");
      if (!btn) {
        console.error('Element with ID "upvote" not found');
        return;
    }
      let disp = document.getElementById("display");
      let post_id = btn.getAttribute("data-post-id");
    
      btn.onclick = function () {
          // Create an AJAX request to send the post_id to PHP
          let xhr = new XMLHttpRequest();
          xhr.open("POST", "<?php echo URLROOT;?>/posts/likepost", true);
          xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
    
          xhr.onreadystatechange = function () {
              if (xhr.readyState === 4 && xhr.status === 200) {
                  // Handle the response from PHP
                  let response = JSON.parse(xhr.responseText);
                  if (response.status === 'liked') {
                      disp.innerHTML = response.likes_count; // Update the like count
                  } else if (response.status === 'unliked') {
                      disp.innerHTML = response.likes_count; // Update the like count
                  }
              }
          };
    
          // Send the post_id as part of the request
          xhr.send("post_id=" + post_id);
      }
    });

Whenever i am trying to run this i am getting following error in my console:

As per this error it is showing error in my another method which is running fine, i am pasting that here for reference as well:

    public function show($id)
        {
                $post = $this->postModel->getPostById($id);
                $user = $this->userModel->getUserById($post->userid);
                $data = [
                'post' => $post,
                'user' => $user,   
                ];
                $this->view('posts/show',$data);
        }