Send message to a connected user - php

Question

I want to send a message from a user (user A) to another user (user B) which those users are connected each other in the database. To be more specific.
We keep the connection of the users in a table in the database which we called friends. In this table we have two columns, username and friend.
I have the code in order to send data between the users but it doesn't perform any checking in order to see if the user A who wants to send a message to the user B are connected to each other. If the users are connected I want to allow them to send the message and if they are not I want to echo a notification that they are not allowed to send a message because they are not connected.
I can understand that I want an if condition where I perform the check to see if the users are connected and have the appropriate code below and if it is not connected then output the notification described above.
How can I create this checking?
I am using php and mysql
HERE IS MY CODE...
<?php
include_once 'header.php';
if (!$loggedin) die();
if (isset($_GET['view'])) {
$view = sanitizeString($_GET['view']);
} else {
$view = $username;
}
if (isset($_POST['text'])){
$text = sanitizeString($_POST['text']);
if ($text != ""){
$pm = substr(sanitizeString($_POST['pm']),0,1);
$time = time();
queryMysql("INSERT INTO messages VALUES(NULL, '$username', '$view', '$pm', $time, '$text')");
}
}
if ($view != "") {
if ($view == $username) {
$name1 = $name2 = "Your";
} else {
$name1 = "<a href='members.php?view=$view'>$view</a>'s";
$name2 = "$view's";
}
echo "<div class='main'><h3>$name1 Messages</h3>";
showProfile($view);
echo <<<_END
<form method='post' action='messages.php?view=$view'>
Type here to leave a message:<br />
<textarea name='text' cols='40' rows='3'></textarea><br />
Public<input type='radio' name='pm' value='0' checked='checked' />
Private<input type='radio' name='pm' value='1' />
<input type='submit' value='Post Message' /></form><br />
_END;
if (isset($_GET['erase'])) {
$erase = sanitizeString($_GET['erase']);
queryMysql("DELETE FROM messages WHERE id=$erase AND recip='$username'");
}
$query = "SELECT * FROM messages WHERE recip='$view' ORDER BY time DESC";
$result = queryMysql($query);
$num = mysql_num_rows($result);
for ($j = 0 ; $j < $num ; ++$j) {
$row = mysql_fetch_row($result);
if ($row[3] == 0 || $row[1] == $username || $row[2] == $username) {
echo date('M jS \'y g:ia:', $row[4]);
echo " <a href='messages.php?view=$row[1]'>$row[1]</a> ";
if ($row[3] == 0) {
echo "wrote: "$row[5]" ";
} else {
echo "whispered: <span class='whisper'>" . ""$row[5]"</span> ";
}
if ($row[2] == $username) {
echo "[<a href='messages.php?view=$view" . "&erase=$row[0]'>erase</a>]";
}
echo "<br>";
}
}
}
if (!$num) {
echo "<br /><span class='info'>No messages yet</span><br /><br />";
}
echo "<br /><a class='button' href='messages.php?view=$view'>Refresh messages</a>";
?>
</div><br /></body></html>

Answer 1

The checking system for my question is the below and it works..
<?php
include_once 'header.php';
if (!$loggedin) die();
if (isset($_GET['view'])) $view = sanitizeString($_GET['view']);
else $view = $username;
$result1 = mysql_num_rows(queryMysql("SELECT username,friend FROM friends
WHERE username='$username' AND friend='$view'"));
$result2 = mysql_num_rows(queryMysql("SELECT username,friend FROM friends
WHERE username='$view' AND friend='$username'"));
if (($result1 + $result2) > 1)
{
//REST OF THE CODE
}
?>
what we are doing is that for the result1 we are checking if the logged in username($username) is connected with the viewed profile ($view) and for the result2 we are doing vice versal, to be more specific we are checking in the result2 that if the username of the viewed profile($view) is connected with the ($username) then in the if statement we check that if those two result has more than one row in the table then they are both connected.
PS: sorry for my bad english