Simple Chat script in PHP, MySQL and Ajax

In this tutorial I will show you how to create a simple but very effective Chat script, and I said effective because unlike the most of the chat scripts this one deletes automatically the old messages from the database. Here is a live demo:

------------------------------
hi
venkat

hi
raja
------------------------------

The chat is refreshed automatically each 30 seconds.

Let`s start: First we need to create a MySQL table with 4 fields:

time - the time when the message was posted (UNIX)
name - the name of the author of the message
ip - the ip of the author of the message
message - the message text


To create the table (I will call it chat) I`we used the following file:
create-table.php


//Connect to MySQL
mysql_connect('host', 'database', 'password')
or die (mysql_error());
//Select database
mysql_select_db('database')
or die (mysql_error());
//Create the table
mysql_query("create table chat(
time int(11) NOT NULL,
name varchar(30) NOT NULL,
ip varchar(15) NOT NULL,
message varchar(255) NOT NULL,
PRIMARY KEY (time)
)") or die (mysql_error());
echo "Complete.";
?>



For the rest of the Chat script we will need 3 more files:
chat.php
send.php
show-messages.php

Let`s start with the chat.php what will contain the forms and all the Ajax scripts what will trigger the other 2 files:
chat.php

//This div will contain the messages

//This div will contain an eventual error message

//This div contains the forms and the send button

Name:

//This div will contain the messages

//This div will contain an eventual error message

//This div contains the forms and the send button

Name:

send.php



//Connect to MySQL
mysql_connect('host', 'database', 'password') or die (1);
//Select database
mysql_select_db('database') or die (2);
//Check if message is empty and send the error code
if(strlen($message) <>
echo 3;
}
//Check if message is too long
else if(strlen($message) > 255){
echo 4;
}
//Check if name is empty
else if(strlen($name) <>
echo 5;
}
//Check if name is too long
else if(strlen($name) > 29){
echo 6;
}
//Check if the name is used by somebody else
else if(mysql_num_rows(mysql_query("select * from chat where name = '" . $name . "' and ip != '" . @$REMOTE_ADDR . "'")) != 0){
echo 7;
}
//If everything is fine
else{
//This array contains the characters what will be removed from the message and name, because else somebody could send redirection script or links
$search = array("<",">",">","<");
//Insert a new row in the chat table
mysql_query("insert into chat values ('" . time() . "', '" . str_replace($search,"",$name) . "', '" . @$REMOTE_ADDR . "', '" . str_replace($search,"",$message) . "')") or die(8);
}
?>

show-messages.php


//Connect to MySQL
mysql_connect('host','database','password');
//Select database
mysql_select_db('database') or die(2);
//Get the first 10 messages ordered by time
$result = mysql_query("select * from chat order by time desc limit 0,10");
$messages = array();
//Loop and get in an array all the rows until there are not more to get
while($row = mysql_fetch_array($result)){
//Put the messages in divs and then in an array
$messages[] = "

" . $row[name] . " - " . date('g:i A M, d Y',$row[time]) . "

" . $row[message] . "

";
//The last posts date
$old = $row[time];
}
//Display the messages in an ascending order, so the newest message will be at the bottom
for($i=9;$i>=0;$i--){
echo $messages[$i];
}
//This is the more important line, this deletes each message older then the 10th message ordered by time is deleted, so the table will never have to store more than 10 messages.
mysql_query("delete from chat where time < " . $old);
?>


And this is it. A very effect chat system what uses only 10 rows of a MySQL table. This chat system can be easily upgraded with admin options or IP bans, smileys and other stuff like this. If you have any question related to this chat system just ASK!