php-single pattern

<code>static private $_instance = NULL;
</code>

When the instance of the class does not exist, this method will create an instance of the class and return this instance. Normally, the name of this method is getInstance

<code>public function getInstance()
{
    if (self::$_instance == NULL) {
        self::$_instance = new SingleTon();
    }
    return self::$_instance;
}
</code>

If the user tries to use new or _clone to create a new object of a class, it will break the restrictions of the singleton mode. Therefore, it is also necessary to declare these two methods as private.

<code>private function __construct(){
}
private function __clone(){
}
</code>

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The above has introduced the php-single pattern, including aspects of it. I hope it will be helpful to friends who are interested in PHP tutorials.