This framework is provided with the CD-ROM. You don’t need to create it from scratch.Also note that the database abstraction uses DB.php from the PEAR. Now let’s create the classes needed to implement this application framework. Creating a Database Abstraction Class Accessing a database using its own API is common in the PHP world. For example, most PHP developers use PHP with MySQL and, therefore, they write code that is specific to the MySQL API found in PHP. There is nothing wrong with this approach if you know that your PHP applica- tions will be used only for the MySQL database server. However, if there is a chance that your applications will be used with other databases such as Oracle, Postgres, and so forth, you need to avoid MySQL-specific API. A developer who has abstracted the database API in a level above the vendor-specific API can enjoy the speed of porting the application to different relational databases. Here, we will cre- ate a class called class.DBI.php that will implement a database abstraction layer for our application framework. Listing 4-1 shows class.DBI.php, which implements the database abstraction using PEAR DB. See http://pear.php.net/manual/en/core.db.php for details on PEAR DB, a unified API for accessing SQL-databases. Listing 4-1: class.DBI.php <?php /* Database abstraction class Purpose: this class provides database abstraction using the PEAR DB package. Continued Chapter 4: Architecture of an Intranet Application 71 07 549669 ch04.qxd 4/4/03 9:24 AM Page 71 Listing 4-1 (Continued) */ define(‘DBI_LOADED’, TRUE); class DBI { var $VERSION = “1.0.0”; function DBI($DB_URL) { $this->db_url = $DB_URL; $this->connect(); if ($this->connected == TRUE) { // set default mode for all resultset $this->dbh->setFetchMode(DB_FETCHMODE_OBJECT); } } function connect() { // connect to the database $status = $this->dbh = DB::connect($this->db_url); if (DB::isError($status)) { $this->connected = FALSE; $this->error = $status->getMessage(); } else { $this->connected = TRUE; } return $this->connected; } function isConnected() 72 Part II: Developing Intranet Solutions 07 549669 ch04.qxd 4/4/03 9:24 AM Page 72 { return $this->connected; } function disconnect() { if (isset($this->dbh)) { $this->dbh->disconnect(); return 1; } else { return 0; } } function query($statement) { $result = $this->dbh->query($statement); if (DB::isError($result)) { $this->setError($result->getMessage()); return null; } else { return $result; } } function setError($msg = null) { global $TABLE_DOES_NOT_EXIST, $TABLE_UNKNOWN_ERROR; $this->error = $msg; if (strpos($msg, ‘no such table’)) { $this->error_type = $TABLE_DOES_NOT_EXIST; } else { Continued Chapter 4: Architecture of an Intranet Application 73 07 549669 ch04.qxd 4/4/03 9:24 AM Page 73 Listing 4-1 (Continued) $this->error_type = $TABLE_UNKNOWN_ERROR; } } function isError() { return (!empty($this->error)) ? 1 : 0; } function isErrorType($type = null) { return ($this->error_type == $type) ? 1 : 0; } function getError() { return $this->error; } function quote($str) { return “‘“ . $str . “‘“; } function apiVersion() { return $VERSION; } } ?> Here are the functions the DBI class implements: ◆ DBI(): This is the constructor method, which creates the instances of the DBI object. For example, here is a script called test_dbi.php that creates a DBI object. <?php // Turn on all error reporting error_reporting(E_ALL); // If you have installed PEAR packages in a different // directory than %DocumentRoot%/pear change the 74 Part II: Developing Intranet Solutions 07 549669 ch04.qxd 4/4/03 9:24 AM Page 74 // setting below. $PEAR_DIR = $_SERVER[‘DOCUMENT_ROOT’] . ‘/pear’ ; // If you have installed PHPLIB in a different // directory than %DocumentRoot%/phplib, change // the setting below. $PHPLIB_DIR = $_SERVER[‘DOCUMENT_ROOT’] . ‘/phplib’; // If you have installed framework directory in // a different directory than // %DocumentRoot%/framework, change the setting below. $APP_FRAMEWORK_DIR=$_SERVER[‘DOCUMENT_ROOT’] . ‘/framework’; // Create a path consisting of the PEAR, // PHPLIB and our application framework // path ($APP_FRAMEWORK_DIR) $PATH = $PEAR_DIR . ‘:’ . $PHPLIB_DIR . ‘:’ . $APP_FRAMEWORK_DIR; // Insert the path in the PHP include_path so that PHP // looks for our PEAR, PHPLIB and application framework // classes in these directories ini_set( ‘include_path’, ‘:’ . $PATH . ‘:’ . ini_get(‘include_path’)); // Now load the DB.php class from PEAR require_once ‘DB.php’; // Now load our DBI class from application framework // directory require_once(‘class.DBI.php’); // Set the database URL to point to a MySQL // database. In this example, the database is // pointing to a MySQL database called auth on // the localhost server, which requires username // (root) and password (foobar) to login $DB_URL = ‘mysql://root:foobar@localhost/auth’; // Create a DBI object using our DBI class // Use the database URL to initialize the object // and make connection to the database $dbi = new DBI($DB_URL); Chapter 4: Architecture of an Intranet Application 75 07 549669 ch04.qxd 4/4/03 9:24 AM Page 75 . its own API is common in the PHP world. For example, most PHP developers use PHP with MySQL and, therefore, they write code that is specific to the MySQL API found in PHP. There is nothing wrong. ; // If you have installed PHPLIB in a different // directory than %DocumentRoot%/phplib, change // the setting below. $PHPLIB_DIR = $_SERVER[‘DOCUMENT_ROOT’] . ‘/phplib’; // If you have installed. // PHPLIB and our application framework // path ($APP_FRAMEWORK_DIR) $PATH = $PEAR_DIR . ‘:’ . $PHPLIB_DIR . ‘:’ . $APP_FRAMEWORK_DIR; // Insert the path in the PHP include_path so that PHP //