PHP custom chat, coding a block function - php

Question

I've tried to build a Block function without any luck, my SQL skills are not as good as I hoped they would be in this case.
I have one table called "messages" and one table called "blocks"
Now, there's 1 file syncing everything to the Chat, what I'm trying to do is IF user 1 has blocked user 2 than user 1's messages should never reach user 2 and user 2's message should not reach user 1. In short term, if you block someone you can't speak to him/her and him/her can't speak to you!
"blocks" table:
id bigint(20)
user_id tinyint(20)
block_id tinyint(20)
"messages" table:
id bigint(20)
timestamp datetime
dest_type varchar(255)
dest_id bigint(20)
source_type varchar(255)
source_id bigint(20)
message_type varchar(255)
message text
in "blocks" user_id is the owners id of the block row.
and block_id is the id that the owner wants to block.
IF "messages.source_id = blocks.block_id OR messages.block_id = blocks.user_id"
THAN dont let the message get trough. I understand that asking someone to code this for me is quite rude but I'm asking, can anyone give this a shot?
here's the sync.php file:
http://pastebin.com/8iiSCXGS
Big thanks!

Answer 1

I haven't delved very deeply into your code, but perhaps this will help.
Let's start with a reduced database structure as follows:
CREATE TABLE `blocks` (
`id` BIGINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
`user_id` INT UNSIGNED NOT NULL,
`block_id` INT UNSIGNED NOT NULL );
INSERT INTO `blocks` (`user_id`,`block_id`) VALUES
(1,2),(3,4),(2,1);
CREATE TABLE `messages` (
`id` BIGINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
`author_id` BIGINT NOT NULL,
`message` TEXT NOT NULL );
INSERT INTO `messages` (`author_id`,`message`) VALUES
(1,"Message from user #1, who has a mutual block in place with user #2"),
(2,"Message from user #2, who has a mutual block in place with user #1"),
(3,"Message from user #3, who has blocked user #4"),
(4,"Message from user #4, who has been blocked by user #3"),
(5,"Message from user #5, who takes no part in all this blocking business");
Now let's suppose user $n visits the website (where 1≤$n≤5). To figure out which messages can be displayed, we need to perform a LEFT JOIN of the messages and blocks tables — i.e., we want to consider every row of messages together with any row of blocks that contains relevant information (specifically, where the author of the message has blocked user $n, or has been blocked by user $n). If $n=1, we have the following:
SELECT * FROM `messages`
LEFT JOIN `blocks`
ON (`author_id`=`block_id` AND `user_id`=1)
OR (`author_id`=`user_id` AND `block_id`=1);
Here's the result of that query:
+----+-----------+-----------------------------------------------------------------------+------+---------+----------+
| id | author_id | message | id | user_id | block_id |
+----+-----------+-----------------------------------------------------------------------+------+---------+----------+
| 1 | 1 | Message from user #1, who has a mutual block in place with user #2 | NULL | NULL | NULL |
| 2 | 2 | Message from user #2, who has a mutual block in place with user #1 | 1 | 1 | 2 |
| 2 | 2 | Message from user #2, who has a mutual block in place with user #1 | 3 | 2 | 1 |
| 3 | 3 | Message from user #3, who has blocked user #4 | NULL | NULL | NULL |
| 4 | 4 | Message from user #4, who has been blocked by user #3 | NULL | NULL | NULL |
| 5 | 5 | Message from user #5, who takes no part in all this blocking business | NULL | NULL | NULL |
+----+-----------+-----------------------------------------------------------------------+------+---------+----------+
6 rows in set (0.00 sec)
As you can see, the rows we want are the ones where the last three columns are NULL, which means there is no blocking rule affecting the display of this particular message to this particular user. So to extract these messages, we simply add WHERE block_id IS NULL to the end of the query:
SELECT * FROM `messages`
LEFT JOIN `blocks`
ON (`author_id`=`block_id` AND `user_id`=1)
OR (`author_id`=`user_id` AND `block_id`=1)
WHERE `block_id` IS NULL;
+----+-----------+-----------------------------------------------------------------------+------+---------+----------+
| id | author_id | message | id | user_id | block_id |
+----+-----------+-----------------------------------------------------------------------+------+---------+----------+
| 1 | 1 | Message from user #1, who has a mutual block in place with user #2 | NULL | NULL | NULL |
| 3 | 3 | Message from user #3, who has blocked user #4 | NULL | NULL | NULL |
| 4 | 4 | Message from user #4, who has been blocked by user #3 | NULL | NULL | NULL |
| 5 | 5 | Message from user #5, who takes no part in all this blocking business | NULL | NULL | NULL |
+----+-----------+-----------------------------------------------------------------------+------+---------+----------+
4 rows in set (0.01 sec)
If you substitute different user IDs into this query, you should get the results you're after.