PHP singleton class structure - Am I doing it right ?

Answer 1

Example of singleton pattern realization in PHP (since 5.3):

/**
 * Singleton pattern implementation
 */
abstract class Singleton {

    /**
     * Collection of instances
     * @var array
     */
    private static $_aInstance = array();

    /**
     * Private constructor
     */
    private function __construct(){}

    /**
     * Get instance of class
     */
    public static function getInstance() {

    // Get name of current class
    $sClassName = get_called_class();

    // Create new instance if necessary
    if( !isset( self::$_aInstance[ $sClassName ] ) )
        self::$_aInstance[ $sClassName ] = new $sClassName();
        $oInstance = self::$_aInstance[ $sClassName ];

        return $oInstance;
    }

    /**
     * Private final clone method
     */
    final private function __clone(){}
}

Example of usage:

class Example extends Singleton {}
$oExample1 = Example::getInstance();
$oExample2 = Example::getInstance();
echo ( is_a( $oExample1, 'Example' ) && $oExample1 === $oExample2)
    ? 'Same' : 'Different', "\n";