Planning our Framework [ 28 ] /** * Private constructor to prevent it being created directly * @access private */ private function __construct() { } /** * singleton method used to access the object * @access public * @return */ public static function singleton() { if( !isset( self::$instance ) ) { $obj = __CLASS__; self::$instance = new $obj; } return self::$instance; } /** * prevent cloning of the object: * issues an E_USER_ERROR if this is attempted */ public function __clone() { trigger_error( 'Cloning the registry is not permitted', E_USER_ERROR ); } The constructor method (which is used to create an instance of this class as an object) is set to private, which means we cannot call it from outside of the class. This is important as it restricts how the object is instantiated, and allows us to control how many copies of it are created. We next have a singleton method; this is used to access the registry. If there is no instance of the object already, then it creates a new instance and stores it within the $instance variable. If the instance variable is already set, then the object (itself) is returned. This material is copyright and is licensed for the sole use by jackie tracey on 23rd February 2010 953 Quincy Drive, , Brick, , 08724 Chapter 2 [ 29 ] Finally, to prevent the object being cloned, we have a trigger_error call, so should we ever add a functionality that clones our registry, we will nd that an E_USER_ERROR error is produced. Registry objects As discussed earlier, the registry on its own is very straightforward, the more complicated aspects are the objects that the registry will actually store and manage access to. These objects include: Database handler User authentication Template management E-mail sending Let's look at creating those objects now. Database Our database object needs to have functionality for: Connecting to the database Managing multiple database connections Performing queries Returning common query information such as number of rows affected, the last insert ID, and so on Caching queries, particularly so we can integrate a result set with the views (through the template handler), and pass it a cache reference, so it can generate the results into the view Making common queries easier (for example, inserts, updates, and deletes) by having the queries pre-formatted within certain methods of the object There is obviously a lot more a database object could do; we will discuss that in a moment. Our database object This database class abstracts the MySQL functions from the rest of the framework into a single le, which manages the database connection: <?php /** * Database management / access class: basic abstraction • • • • • • • • • • This material is copyright and is licensed for the sole use by jackie tracey on 23rd February 2010 953 Quincy Drive, , Brick, , 08724 Planning our Framework [ 30 ] * * @author Michael Peacock * @version 1.0 */ class mysqldatabase { /** * Allows multiple database connections * each connection is stored as an element in the array, * and the active connection is maintained in a variable (see below) */ private $connections = array(); /** * Tells the DB object which connection to use * setActiveConnection($id) allows us to change this */ private $activeConnection = 0; /** * Queries which have been executed and the results cached for * later, primarily for use within the template engine */ private $queryCache = array(); /** * Data which has been prepared and then cached for later usage, * primarily within the template engine */ private $dataCache = array(); /** * Number of queries made during execution process */ private $queryCounter = 0; /** * Record of the last query */ private $last; /** * Construct our database object */ public function __construct() { } This material is copyright and is licensed for the sole use by jackie tracey on 23rd February 2010 953 Quincy Drive, , Brick, , 08724 Chapter 2 [ 31 ] Let's look through what it does, method by method: newConnection: This method creates a new connection to a database. This is separate from the constructor for two reasons: rstly, if it were in the constructor, we would need to pass the connection details to it, which would mean it would need to be created separately from the other objects within the registry. Secondly, this method allows us to maintain several connections to databases within the same object. /** * Create a new database connection * @param String database hostname * @param String database username * @param String database password * @param String database we are using * @return int the id of the new connection */ public function newConnection( $host, $user, $password, $database ) { $this->connections[] = new mysqli( $host, $user, $password, $database ); $connection_id = count( $this->connections )-1; if( mysqli_connect_errno() ) { trigger_error('Error connecting to host. ' .$this->connections[$connection_id]->error, E_USER_ERROR); } return $connection_id; } closeConnection: This method closes the active connection (while there are multiple connections within the object, the current object being used is stored as a variable to keep track of it). /** * Close the active connection * @return void */ public function closeConnection() { $this->connections[$this->activeConnection]->close(); } • • This material is copyright and is licensed for the sole use by jackie tracey on 23rd February 2010 953 Quincy Drive, , Brick, , 08724 Planning our Framework [ 32 ] setActiveConnection: This method allows us to toggle which database connection is the active one to be used. /** * Change which database connection is actively used for the * next operation * @param int the new connection id * @return void */ public function setActiveConnection( int $new ) { $this->activeConnection = $new; } cacheQuery: This method allows us to store a query to be processed later, primarily to be replaced in a loop into the view. /** * Store a query in the query cache for processing later * @param String the query string * @return the pointed to the query in the cache */ public function cacheQuery( $queryStr ) { if( !$result = $this->connections [$this->activeConnection]->query( $queryStr ) ) { trigger_error('Error executing and caching query: ' .$this->connections[$this->activeConnection] ->error, E_USER_ERROR); return -1; } else { $this->queryCache[] = $result; return count($this->queryCache)-1; } } numRowsFromCache: This method tells us the number of rows a cached query contains. /** * Get the number of rows from the cache * @param int the query cache pointer • • • This material is copyright and is licensed for the sole use by jackie tracey on 23rd February 2010 953 Quincy Drive, , Brick, , 08724 . connection: < ?php /** * Database management / access class: basic abstraction • • • • • • • • • • This material is copyright and is licensed for the sole use by jackie tracey on 23rd February 2010 953 . material is copyright and is licensed for the sole use by jackie tracey on 23rd February 2010 953 Quincy Drive, , Brick, , 08724 Chapter 2 [ 29 ] Finally, to prevent the object being cloned,. material is copyright and is licensed for the sole use by jackie tracey on 23rd February 2010 953 Quincy Drive, , Brick, , 08724 Chapter 2 [ 31 ] Let's look through what it does, method