PHP comment system - echo matching foreign key and id - php

Question

I'm creating a image gallery where people can add comments to each uploaded image.
I've made a db tabel for all comments including a foreign key to match the image table.
My SQL variable looks like this and seems to work fine:
$all_comments_one_image_sql="
SELECT userimage.id, image_id, comment, id, comment_date
FROM userimage, image_comment
WHERE image_comment.image_id=userimage.id
ORDER BY comment_id DESC
";
But when I'm doing my while function for all my gallery images, where and how would I echo the right comments to each image?

Answer 1

You should be doing a left join like this:
select userimage.id,
com.image_id,
com.comment,
com.id,
com.comment_date
FROM userimage
LEFT JOIN image_comment as com ON com.image_id=userimage.id
WHERE userimage.id = ?
ORDER BY com.id DESC

Answer 2

First of all create a function for getting image comments:
function getImageComments($imageId){
$query = "SELECT userimage.id, image_id, comment, id, comment_date
FROM userimage
LEFT JOIN image_comment
ON image_comment.image_id=userimage.id
WHERE image_id = $imageId
ORDER BY comment_id DESC
";
mysql_query($query);
return mysql_fetch....
}
I also redo your query for better performance.
So whnever you are loading an image, call the function with the proper image id and get its comments.

Answer 3

You have to check for the right image_id
$all_comments_one_image_sql = "
SELECT userimage.id, image_id, comment, id, comment_date
FROM userimage, image_comment
WHERE image_comment.image_id=userimage.id AND image_id = ?
ORDER BY comment_id DESC
";
where ? is the id of the image you want to Show comments - if you use pdo, you can just bind the image id and don't have to care about escaping.
If you have a summary page for all images, you can add the results in an assoc array, where the key is your image id
$comments[] = array();
while ($row = $res->fetch()) {
if (empty($comments[$row->image_id])) {
$comments[$row->image_id] = array();
}
$comments[$row->image_id][] = $row;
}
To show the comments, you can just look, if $comments[$image_id] is an array and show the conent