Taking values from a table and echoing them out - php

Question

I am working on a messaging system for one of my sites and I'm having a lot of issues with getting the messages to show up. For some reason I can't get the syntax right so that it will take every single value that matches the receiver_id will display if the user_id matches the receiver_id. I had it working fine on my windows test machine, but when I uploaded it to my ubuntu server it broke. So now I'm trying to fix the code. What I have is this:
$m = "SELECT m.message_id, m.receiver_id, m.sender_id, m.subject, m.body, m.posted, u.id, u.username FROM messages m, users u WHERE u.id = {$_SESSION['id']}";
$b = mysqli_query($dbc, $m);
?>
<div class="mailbox">
Inbox<br />
Sent<br />
</div>
<div class="mailbox">
<h2>Messages for <?php echo $_SESSION['username']; ?></h2>
<?php echo output_message($message); ?>
<div id="messages">
<?php
if (mysqli_num_rows($b) > 0) {
while ($mess_row = mysqli_fetch_array($b, MYSQLI_NUM)) {
$u = "SELECT * FROM users WHERE id={$mess_row[1]}";
$rec = mysqli_query($dbc, $u);
$rec_row = mysqli_fetch_array($rec, MYSQLI_NUM);
$s = "SELECT * FROM users WHERE id={$mess_row[2]}";
$send = mysqli_query($dbc, $r);
$send_row = mysqli_fetch_array($send, MYSQLI_NUM);
echo "$mess_row[3] Posted by: <b>$send_row[1]</b> on: $mess_row[5]<br /><hr />";
}
} else {
echo "No messages.";
}
What am I doing wrong? I thought I had it fixed but then it just spit out the same record five times. I tried grouping which only gave me 1 record. I tried moving the $s call outside the while loop but I'm not able to draw on the sender's user_id that way. I just don't know what to do and I've searched all over for the past several hours and I can't find exactly what I'm looking for, or else I'm not typing the question right.
Thanks in advance.

Answer 1

Use a JOIN to get everything in one query:
$m = "SELECT m.message_id, m.receiver_id, m.sender_id, m.subject, m.body, m.posted, s.username sender_name, r.username receiver_name
FROM messages m
JOIN users r ON r.id = m.receiver_id
JOIN users s ON s.id = m.sender_id
WHERE u.id = {$_SESSION['id']}";

Answer 2

I apologize for hastily throwing this together. Hope it helps.
Use this as your query, then you won't have to go through and do that horrible extra set of queries to get the user info.
$id = $dbc->real_escape_string($_SESSION['id']);
$m = "SELECT m.message_id, m.receiver_id, m.sender_id, m.subject, m.body, m.posted, u.id, u.username
FROM messages m
INNER JOIN users u ON m.receiver_id=u.id
WHERE u.id = '$id';";
Extra note: Your need to escape your session id string. I'd probably also verify it is just numbers using a regex.
edit: Use #Barmar answers query in place of mine. I'd still add the escaping/regex though.