Viewing file:  chat.class.php (5.21 KB) -rw-rw-rw-
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<?php
// load configuration file
require_once('config.php');
// load error handling module
require_once('error_handler.php');
// class that contains server-side chat functionality
class Chat
{
// database handler
private $mMysqli;
// constructor opens database connection
function __construct()
{
// connect to the database
$this->mMysqli = new mysqli(DB_HOST, DB_USER, DB_PASSWORD,
DB_DATABASE);
}
// destructor closes database connection
public function __destruct()
{
$this->mMysqli->close();
}
// truncates the table containing the messages
public function deleteMessages()
{
// build the SQL query that adds a new message to the server
$query = 'TRUNCATE TABLE chat';
// execute the SQL query
$result = $this->mMysqli->query($query);
}
/*
The postMessages method inserts a message into the database
- $name represents the name of the user that posted the message
- $messsage is the posted message
- $color contains the color chosen by the user
*/
public function postMessage($name, $message, $color)
{
// escape the variable data for safely adding them to the database
$name = $this->mMysqli->real_escape_string($name);
$message = $this->mMysqli->real_escape_string($message);
$color = $this->mMysqli->real_escape_string($color);
// build the SQL query that adds a new message to the server
$query = 'INSERT INTO chat(posted_on, user_name, message, color) ' .
'VALUES (NOW(), "' . $name . '" , "' . $message .
'","' . $color . '")';
// execute the SQL query
$result = $this->mMysqli->query($query);
}
/*
The retrieveNewMessages method retrieves the new messages that have
been posted to the server.
- the $id parameter is sent by the client and it
represents the id of the last message received by the client. Messages
more recent by $id will be fetched from the database and returned to
the client in XML format.
*/
public function retrieveNewMessages($id=0)
{
// escape the variable data
$id = $this->mMysqli->real_escape_string($id);
// compose the SQL query that retrieves new messages
if($id>0)
{
// retrieve messages newer than $id
$query =
'SELECT chat_id, user_name, message, color, ' .
' DATE_FORMAT(posted_on, "%Y-%m-%d %H:%i:%s") ' .
' AS posted_on ' .
' FROM chat WHERE chat_id > ' . $id .
' ORDER BY chat_id ASC';
}
else
{
// on the first load only retrieve the last 50 messages from server
$query =
' SELECT chat_id, user_name, message, color, posted_on FROM ' .
' (SELECT chat_id, user_name, message, color, ' .
' DATE_FORMAT(posted_on, "%Y-%m-%d %H:%i:%s") AS posted_on ' .
' FROM chat ' .
' ORDER BY chat_id DESC ' .
' LIMIT 50) AS Last50' .
' ORDER BY chat_id ASC';
}
// execute the query
$result = $this->mMysqli->query($query);
// build the XML response
$response = '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>';
$response .= '<response>';
// output the clear flag
$response .= $this->isDatabaseCleared($id);
// check to see if we have any results
if($result->num_rows)
{
// loop through all the fetched messages to build the result message
while ($row = $result->fetch_array(MYSQLI_ASSOC))
{
$id = $row['chat_id'];
$color = htmlspecialchars ($row['color']);
$userName = htmlspecialchars ($row['user_name']);
$time = htmlspecialchars \\\\\\\($row['posted_on']);
$message = htmlspecialchars ($row['message']);
$response .= '<id>' . $id . '</id>' .
'<color><![CDATA[' . $color . ']]></color>' .
'<time>' . $time . '</time>' .
'<name><![CDATA[' . $userName . ']]></name>' .
'<message><![CDATA[' . $message . ']]></message>';
}
// close the database connection as soon as possible
$result->close();
}
// finish the XML response and return it
$response = $response . '</response>';
return $response;
}
/*
The isDatabaseCleared method checks to see if the database has been
cleared since last call to the server
- the $id parameter contains the id of the last message received by
the client
*/
private function isDatabaseCleared($id)
{
if($id>0)
{
// by checking the number of rows with ids smaller than the client's
// last id we check to see if a truncate operation was performed in
// the meantime
$check_clear = 'SELECT count(*) old FROM chat where chat_id<=' . $id;
$result = $this->mMysqli->query($check_clear);
$row = $result->fetch_array(MYSQLI_ASSOC);
// if a truncate operation occured the whiteboard needs to be reset
if($row['old']==0)
return '<clear>true</clear>';
}
return '<clear>false</clear>';
}
}
?>
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