PHP Single-instance mode

The singleton mode is primarily used for database connections, ensuring that the database has only one instance of a class and provides this instance to the entire system. This prevents new operations from consuming resources while avoiding too many connection information in the database.There are three points: 1. There must be only one instance. 2. This instance must be created automatically. 3. This instance must be provided to the system as a whole. <?    classMySQL{Privete Static$instance;//Save Instance        The //constructor is declared private to prevent the object from being created directlyPrivete function__construct(){            //Instantiation        }        //Singleton method to determine if it has been instantiated, and only instantiate once         PublicStaticfunctiongetinstance (){            if(!isset( Self::$instance)){ Self::$instance=New Self();            }            return Self::$instance;        }        //Prevent cloning objects        Privatefunction__clone(){            Trigger_error("Not allow to clone.");         }        functionTest(){            Echo"Test" ;        }    }    $conn= MySQL::getinstance();    $conn -Test();?>

PHP Single-instance mode