In this tutorial I will show you how to create a shoutbox and put in some functionality to attempt to keep a user from filling up your database and overloading your server.
The first thing we'll need of course is a table to store the messages, it will also store the ip of the user posting so they cannot post more than once over a specific time period we will also put in a redirect to secure it a little bit more, this is also nice because by refreshing the page they won't be able to resend the information. We'll need a column to store the username they enter and one to store their message also.
CREATE TABLE shoutbox {
           id INT NOT NULL AUTO_INCREMENT,
           username VARCHAR(20),
           message TEXT,
           user_ip VARCHAR(16),
           date TIMESTAMP;
           PRIMARY KEY(id)
       };
That is all you'll need to start; a column to store their username, one for the message, one for their ip and one to store the timestamp of the date posted. Now we'll need to create a form so they can send their messages. It will only need two text fields and a submit button.

html:

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<form action="<? echo $_SERVER['PHP_SELF']; ?> method="post">
    Username: <input type="text" name="username"><br>
    Message: <input type="text" mame="message"><br>
    <input type="submit" value="submit">
</form>

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Next we will need to create a simple php script to process their submit and insert the info into the database. We will use $_SERVER['REMOTE_ADDR'] to get their ip address and use the php time() function to get the timestamp of their post. Ok now some code to process the submit:

php:

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<?php
if($_POST) /* check for a form submit */
{
    $time = time(); /* get the current timestamp */
    
    /*
    * insert their info into database using
    * $_SERVER['REMOTE_ADDR'] for their ip,
    * also use addslashes to escape characters
    * like quotes etc.
    */
    $sql = "INSERT INTO shoutbox(username, message, user_ip, date) VALUES(
            '".addslashes($username)."', '".addslashes($message)."',
            '".$_SERVER['REMOTE_ADDR']."', '$time'";
    mysql_query($sql) or die(mysql_error());
    
    /*
    * Pause for three seconds and then redirect
    * them back to the main page, this is helpful
    * so they cannot resubmit info and if they hit
    * refresh they dont get a pesky post resend message
    */
    print("Redirecting three seconds.");
    sleep(3);
    header("Location: ./index.php");
}
?>


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