Creating A Guestbook Using PHP and MySQL

You've seen it at least once right? Guestbook is one of the most common thing to find in a website. In this tutorial we'll create a guestbook using PHP and MySQL. I have split this tutorial into two section, each covering a specific feature of the guestbook. - Creating The Sign-Guestbook Form
This part will cover creating the database tables, the guestbook form and the process of saving the entry to database
- Viewing The Entries
You want to see the guestbook entries of course. This section covers fetching the entries from database and put int into an HTML table. You will also learn to show the entries in multiple pages using MySQL paging.

I think you should take a quick look what the finished guestbook look like. Just click here to see it. Creating The Sign-Guestbook Form
We start by creating the table to store the data, guestbook. There are six fields in the guestbook table: 1. id : the unique identifier for an entry in the guestbook
2. name : the visitor's name
3. email : visitor's email address
4. url : visitor's website url, if she has one
5. message : the message
6. entry_date : when did this entry added I have put the SQL query needed to create the table in guestbook.txt. Below is the HTML form code. It's pretty simple, we have text box for name, email and url plus a textarea to hold the message. The submit button is attached with a javascript function because we want to check the input values before the page is submitted.
Below is the javascript code to check the input form. The [color=144273]checkForm()[/color] function is called when the "Sign Guestbook" button is clicked.

The mandatory fields are name and message so if either is empty we pop an alert box to tell the visitor to enter the name and message. Email is not a mandatory field so we only check if in an email address is entered but we won't complain if there's none .

After the form is submitted our job turns to saving the input into the database. In the code below I include config.php and opendb.php which contain the database configuration and the code needed to open a connection to MySQL. It's a good practice to put these actions in separate file. That way everytime you need to connect to MySQL you can include these files instead of rewriting the code. Also you can change the database information from just one file instead of changing it in every file that use MySQL. To see what the content of config.php, opendb.php and closedb.php
config.php
opendb.php


The script check if the $_POST['btnSign'] variable is set. If it is then the "Sign Guestbook" button must have been clicked and now we can read name, email, url and message from the $_POST global variable. After that we create an INSERT query string and execute the query using mysql_query(). Sometimes a message can contain single quotes, we need to escape these single quotes ( replacing it with \' ) otherwise MySQL will think that it's the end of a string and the query will fail. We use the addslashes() function to escape the string. Unfortunately some web hosts set the magic_quotes_gpc setting on. This will make values containing single-quotes in $_GET, $_POST and $_COOKIE will be automatically escaped. If we use addslashes() when the string is already escaped the result would be a mess. To check if magic_quotes_gpc is On use get_magic_quotes_gpc(). If it returns true then we don't have to call addslashes(). Ok, now affter all input is ready we can build the query string to enter the name, email, url, message and entry date. Note that for the entry_date field we use current_date. This is not a PHP variable or function, it's a built in MySQL function that returns ( guess what? ) the current date. You also see that I didn't explicitly insert the value of id field. This is because id is set as auto_increment so when we insert a new row into the table a new value for id is automatically generated ( incremented for each new row). After inserting the new guestbook entry the next thing we do is redirect back to current page using header('Location: ' . $_SERVER['REQUEST_URI']); Why? The redirect is just to prevent double submission. Suppose we don't use the redirect and the visitor hit the refresh button after signing up the guestbook then the form will be submitted again. Note : If you get this kind of error message Warning: Cannot modify header information - headers already sent by (output started at C:\webroot\guestbook\library\config.php:7) in C:\webroot\guestbook\guestbook.php on line 43 this mean the redirect failed because you already sent something to the browser. I got the error message above because i "accidentally" have a space right after the closing tag ( ?> ) in config.php. By removing this space the error is fixed. This kind of errror is actually very common to see when your code is sending headers and fixing it is easy like the example above. Just check the file pointed by the error message and see if you accidentally sent ( print ) anyhing to the browser.
-------------------------------------------------------------------------------- Pheww, we just finished the first part of our guestbook. Now it's time to create the script which will show the guestbook entries. We'll also try to split the entries into multiple pages when they are too much to be shown in one page.