The singleton pattern ensures that there is only one instance of a class;
1. Static member variables save the only instance of the class
2. Declare the constructor and clone method as private to prevent new instances
3. Provide a public static method to access this instance and return a reference to the unique instance
class InstanceDemo
{
private static $_instance;//Static member variables save the only instance
private function __construct()//Constructor function
{
echo 'I am Construceted';
}
public static function GetInstance()
{
if(!isset(self::$_instance))
{
$c=__CLASS__;
}
return self::$_instance;
}
//Override the __clone() method and disable cloning
private function __clone()
{
echo "clone prohibited";
}
function test()
{
echo("test instance");
}
}
//Call the static public method to get the only instance
$test = InstanceDemo::GetInstance();
$test->test();
//Cloneing is prohibited
$test_clone = clone $test;
?>
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