PHP - Guestbook Class

This class can be used to setup a simple guestbook. The class allows you to add comments, get comments and delete comments. This example uses a database to store the comments.

1. <?php
2.  
3.     class GuestBook {
4.         private $_pdo = null;
5.  
6.         public function __construct($host, $dbname, $username, $password){
7.             try{
8.                 $this->_pdo = new PDO("mysql:host=$host;dbname=$dbname", $username, $password);
9.             }catch(PDOException $e){
10.                 throw new PDOException($e->getMessage(), $e->getCode(), $e);
11.             }
12.         }
13.  
14.         public function addComment($author, $subject, $comment){
15.             if ($this->_pdo){
16.                 $stm = $this->_pdo->prepare("INSERT INTO guest_book (author,subject,comment,posted_date) VALUES (:author,:subject,:comment,NOW())");
17.                 $stm->bindParam(':author', $author);
18.                 $stm->bindParam(':subject', $subject);
19.                 $stm->bindParam(':comment', $comment);
20.  
21.                 if ($stm->execute()){
22.                     return true;
23.                 }
24.             }
25.             return false;
26.         }
27.  
28.         public function getComments(){
29.             if ($this->_pdo){
30.                 $stm = $this->_pdo->prepare("SELECT * FROM guest_book");
31.  
32.                 if ($stm->execute()){
33.                     return $stm->fetchAll(PDO::FETCH_OBJ);
34.                 }
35.             }
36.             return false;
37.         }
38.  
39.         public function getCommentById($comment_id){
40.             if ($this->_pdo){
41.                 $stm = $this->_pdo->prepare("SELECT * FROM guest_book WHERE comment_id=$comment_id");
42.  
43.                 if ($stm->execute()){
44.                     return $stm->fetch(PDO::FETCH_OBJ);
45.                 }
46.             }
47.             return false;
48.         }
49.  
50.         public function deleteCommentById($comment_id){
51.             if ($this->_pdo){
52.                 $stm = $this->_pdo->prepare("DELETE FROM guest_book WHERE comment_id=$comment_id");
53.  
54.                 if ($stm->execute()){
55.                     return true;
56.                 }
57.             }
58.             return false;
59.         }
60.     }
61.  
62.     // Example usage
63.  
64.     try{
65.         $book = new GuestBook('localhost', 'database', 'username', 'password');
66.  
67.         // Add a new comment
68.         $book->addComment('John Smith', 'Hello', 'This is a comment');
69.  
70.         // Get all comments
71.         $comments = $book->getComments();
72.  
73.         // Get comment by comment id
74.         $comment = $book->getCommentById(1);
75.  
76.         // Delete comment by comment id
77.         $book->deleteCommentById(2);
78.  
79.     }catch(PDOException $e){
80.         // Print error message
81.         echo $e->getMessage();
82.     }
83. ?>
84.  
85. //guest_book.sql
86.  
87. DROP TABLE IF EXISTS guest_book;
88. CREATE TABLE guest_book (
89.   comment_id int(11) NOT NULL AUTO_INCREMENT,
90.   author varchar(80) DEFAULT NULL,
91.   subject varchar(50) DEFAULT NULL,
92.   comment text NOT NULL,
93.   posted_date datetime NOT NULL,
94.   PRIMARY KEY (comment_id)
95. )