Cannot retrieve column information from database - php

Question

I have two tables, namely user_info and comments. I want to join the tables, so i can relate the user_id from the from comments after the inner join has happened, which will join based on the id columns. The whole reason for this is so i can find out what the id is of a user who posts a comment on a users profile, which i store in user_id.
SHOW CREATE TABLE user_info
CREATE TABLE `user_info` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`username` varchar(12) COLLATE utf8_unicode_ci NOT NULL,
`pass` varchar(40) COLLATE utf8_unicode_ci DEFAULT NULL,
`joined` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
PRIMARY KEY (`id`),
UNIQUE KEY `username` (`username`))
ENGINE=InnoDB AUTO_INCREMENT=64 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci'
SHOW CREATE TABLE comments
'CREATE TABLE `comments` (
`id` int(11) DEFAULT NULL,
`comment` text COLLATE utf8_unicode_ci,
`date_posted` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
`user_id` int(11) DEFAULT NULL)
ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci'
The query code
try {
$result = $db->prepare("SELECT user_id
FROM comments
INNER JOIN user_info USING (id)
WHERE id = :user");
$result->bindParam(':user', $post_session_user_id);
$result->execute();
$comment_details = $result->fetch();
}
How comment_details is stored
$comment_id = $comment_details[0];
and then i do a var_dump that returns NULL
var_dump($comment_id);
Any ideas what is wrong?

Answer 1

I think you should not be using USING as that works only when you have 2 fields, one in each table both having the same name.
In your tables comment.user_id holds the user_info.id
So your query should probably be
SELECT user_id
FROM comments
INNER JOIN user_info ON user_info.id = comments.user_id
WHERE comments.id = :user