paul dot maddox at gmail dot com 27-Aug-2009 12:54

pattern singleton in PDO.php

I decided to create a singleton wrapper for PDO that ensures only one instance is ever used.
It uses PHP 5.3.0's __callStatic functionality to pass on statically called methods to PDO.

This means you can just call it statically from anywhere without having to initiate or define the object.

Usage examples:

<?php
DB::exec("DELETE FROM Blah");

foreach( DB::query("SELECT * FROM Blah") as $row){
        print_r($row);
}
?>

Code:

<?php

class DB {
   
    private static $objInstance;
   
    /*
     * Class Constructor - Create a new database connection if one doesn't exist
     * Set to private so no-one can create a new instance via ' = new DB();'
     */
    private function __construct() {}
   
    /*
     * Like the constructor, we make __clone private so nobody can clone the instance
     */
    private function __clone() {}
   
    /*
     * Returns DB instance or create initial connection
     * @param
     * @return $objInstance;
     */
    public static function getInstance(  ) {
           
        if(!self::$objInstance){
            self::$objInstance = new PDO(DB_DSN, DB_USER, DB_PASS);
            self::$objInstance->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        }
       
        return self::$objInstance;
   
    } # end method
   
    /*
     * Passes on any static calls to this class onto the singleton PDO instance
     * @param $chrMethod, $arrArguments
     * @return $mix
     */
    final public static function __callStatic( $chrMethod, $arrArguments ) {
           
        $objInstance = self::getInstance();
       
        return call_user_func_array(array($objInstance, $chrMethod), $arrArguments);
       
    } # end method
   
}
?>