PHP Blog Query

[swibit]

I've been following the blog with commenting tutorial but when it comes to the get posts query, I get the error:
[syntax=sql]You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '$sql= "SELECT
'posts'.'post_id' AS id,
'posts'.'post_head' AS head,
' at line 1: [/syntax]

My query code is:
[syntax=sql] $sql = "SELECT
'posts'.'post_id' AS 'id',
'posts'.'post_head' AS 'head',
LEFT('posts'.'post_body',512) AS 'blogsummary',
'posts'.'post_user' AS 'user',
DATE_FORMAT('posts'.'post_date', '%d/%m/%Y %H:%i:%s') AS 'date',
'comments'.'total_comments',
DATE_FORMAT('comments'.'last_comment', '%d/%m/%Y %H:%i:%s') AS 'last_comment'
FROM 'posts'
LEFT JOIN (
SELECT
'post_id',
COUNT('comment_id') AS 'total_comments',
MAX('comment_date') AS 'last_comment'
FROM 'comments'
GROUP BY 'post_id'
) AS 'comments'
ON 'posts'.'post_id' = 'comments'.'post_id'
ORDER BY 'posts'.'post_date' DESC";[/syntax]

I can't see what I've done wrong within my code

[ExtremeGaming]

Change all the apostrophes around your column names to backticks `

[swibit]

So the code should now be like this?
[syntax=sql] function get_posts() {
$sql = "SELECT
`posts`.`post_id` AS `id`,
`posts`.`post_title` AS `title`,
LEFT(`posts.post_body`, 512) AS `preview`,
`posts`.`post_user` AS `user`,
DATE_FORMAT(`posts`.`post_date`, `%d/%m/%Y %H:%i:%s`) AS `date`,
`comments`.`total_comments`,
DATE_FORMAT(`comments`.`last_comment`,`%d/%m/%Y %H:%i:%s`) AS `last_comment`
FROM `posts`
LEFT JOIN (
SELECT
`post_id`,
COUNT(`comment_id`) AS `total_comments`,
MAX(`comment_date`) AS `last_comment`
FROM `comments`
GROUP BY `post_id`
) AS `comments`
ON `posts`.`post_id` = `comments`.`post_id`
ORDER BY `posts`.`post_date` DESC";

$posts = mysql_query($sql);

$rows = array();
while (($row = mysql_fetch_assoc($posts)) !== false) {
$rows[] = array(
`id` => $row[`id`],
`title` => $row[`title`],
`preview` => $row[`preview`],
`user` => $row[`user`],
`date` => $row[`date`],
`total_comments` => ($row[`total_comments`] === null) ? 0 : $row[`total_comments`],
`last_comment` => ($row[`last_comment`] === null) ? `never` : $row[`last_comment`]
);
}

return $rows;
[/syntax]

[ExtremeGaming]

I believe your query should be like this. I have never needed to do such a query before so I don't know.
[syntax=sql] function get_posts() {
$sql = "SELECT
`posts`.`post_id` AS `id`,
`posts`.`post_title` AS `title`,
LEFT(`posts.post_body`, 512) AS `preview`,
`posts`.`post_user` AS `user`,
DATE_FORMAT(`posts`.`post_date`, '%d/%m/%Y %H:%i:%s') AS `date`,
`comments`.`total_comments`,
DATE_FORMAT(`comments`.`last_comment`,'%d/%m/%Y %H:%i:%s') AS `last_comment`
FROM `posts`
LEFT JOIN (
SELECT
`post_id`,
COUNT(`comment_id`) AS `total_comments`,
MAX(`comment_date`) AS `last_comment`
FROM `comments`
GROUP BY `post_id`
) AS `comments`
ON `posts`.`post_id` = `comments`.`post_id`
ORDER BY `posts`.`post_date` DESC";
[/syntax]