| 1: | <?php |
| 2: | |
| 3: | namespace ngatngay\designpattern; |
| 4: | |
| 5: | use Exception; |
| 6: | |
| 7: | class singleton |
| 8: | { |
| 9: | private static ?singleton $instance = null; |
| 10: | |
| 11: | /** |
| 12: | * gets the instance via lazy initialization (created on first usage) |
| 13: | */ |
| 14: | public static function get_instance(): singleton |
| 15: | { |
| 16: | if (self::$instance === null) { |
| 17: | self::$instance = new self(); |
| 18: | } |
| 19: | |
| 20: | return self::$instance; |
| 21: | } |
| 22: | |
| 23: | /** |
| 24: | * is not allowed to call from outside to prevent from creating multiple instances, |
| 25: | * to use the singleton, you have to obtain the instance from Singleton::getInstance() instead |
| 26: | */ |
| 27: | private function __construct() |
| 28: | { |
| 29: | } |
| 30: | |
| 31: | /** |
| 32: | * prevent the instance from being cloned (which would create a second instance of it) |
| 33: | */ |
| 34: | private function __clone() |
| 35: | { |
| 36: | } |
| 37: | |
| 38: | /** |
| 39: | * prevent from being unserialized (which would create a second instance of it) |
| 40: | */ |
| 41: | public function __wakeup() |
| 42: | { |
| 43: | throw new Exception("Cannot unserialize singleton"); |
| 44: | } |
| 45: | } |