Join column from one table to another column in other table CodeIgniter - php

Question

I've got 2 Tables that I want some of the columns to auto update when the other one gets data from user.
Here is my scenario: User registers and his details go to "users" Table.
The registered user can now make a post. When he makes a post his post goes to "posts" table.
Now I want to display the users "username" when he/she makes a post.
So, conclusion is that I want the column "username" from table "users" to automatically synchronize with column "username" from table "posts". So that once a user makes a post, it will see that a specific user made a post.
Here's how i will implement it
<?php foreach ($posts as $post) : ?>
<div class="row">
<div class="col-md-3">
<img class="post-thumb img-fluid" src="<?php echo site_url();
?>assets/images/posts/<?php echo $post['post_image']; ?>">
</div>
<div class="col-md-9">
<h3><?php echo $post['title'];?></h3>
<small class="post-date">Posted on: <?php echo
$post['created_at']; ?>
in <strong><?php echo $post['category_name']?></strong> by
<strong><?php echo $post['username']?></strong></small><br>
<?php echo word_limiter($post['body'], 50); ?>
<br><br>
<p><a class="btn btn-info" href="<?php echo
site_url('/posts/'.$post['slug']);?>"
>Read More</a></p>
</div>
</div>
<?php endforeach; ?>
Here is a function I tried, but it doesn't update my "posts" table column "username" when I make a post.
public function get_posts($slug = FALSE){
if ($slug === FALSE){
$this->db->order_by('posts.id', 'DESC');
$this->db->join('categories', 'categories.id =
posts.category_id');
$this->db->join('users', 'users.username = posts.username');
$query = $this->db->get('posts');
return $query->result_array();
}
$query = $this->db->get_where('posts', array('slug' => $slug));
return $query->row_array();
}
Here are the DB tables
CREATE TABLE `posts` (
`id` int(11) NOT NULL,
`category_id` int(11) NOT NULL,
`user_id` int(11) NOT NULL,
`username` varchar(255) NOT NULL,
`posted_by` varchar(255) NOT NULL,
`title` varchar(255) NOT NULL,
`slug` varchar(255) NOT NULL,
`body` text NOT NULL,
`post_image` varchar(255) NOT NULL,
`created_at` datetime NOT NULL DEFAULT current_timestamp()
) ENGINE=MyISAM DEFAULT CHARSET=latin1;
CREATE TABLE `users` (
`id` int(11) NOT NULL,
`name` varchar(255) NOT NULL,
`email` varchar(255) NOT NULL,
`username` varchar(255) NOT NULL,
`password` varchar(255) NOT NULL,
`register_date` timestamp NOT NULL DEFAULT current_timestamp()
) ENGINE=MyISAM DEFAULT CHARSET=latin1;
There is no error, just no result.
Any advice or help will be appreciated.
EDIT:
I've managed to make a "get_username" function. But I'm not sure why its not working and how to create a loop for it to loop through posts that have been made. Please see code below
public function get_username(){
$username = $this->db->query("
SELECT u.username AS username
FROM users u
LEFT JOIN posts p
ON u.id = p.user_id
WHERE p.id = ?"
, array('id')
)->row_array();
return $username['username'];
}
I get error saying:
A PHP Error was encountered
Severity: Notice
Message: Undefined index: username
Filename: posts/index.php
Line Number: 19

Answer 1

Your get_username() method takes no parameters - what if you wanted to get id of 5? or 20? Currently you have no ability to specify what id to query. The current query, results in:
LEFT JOIN posts p ON u.id = p.user_id WHERE p.id = 'id'
As it's passing a string literally called id, whereas what you actually want, is to pass a parameter with the associated ID to query.
/**
*
**/
public function get_username( int $userId )
{
$username = $this->db->query("
SELECT u.username AS username
FROM users u
LEFT JOIN posts p
ON u.id = p.user_id
WHERE p.id = ?"
, array( $userId )
)->row_array();
return $username['username'];
}