How the PHP subclass accesses the static method of the parent class

1. Subclass internal access to the parent class static member property or method, using Parent::method ()/self::method ()
Note: $this->staticproperty (the static property of the parent class cannot be accessed through $this (subclass instance), there will be an error: PHP Strict standards:accessing static Properties person :: $country as non static in,php notice:undefined property:)
2. Sub-class external
1. Subclass Name:: Method ()
2. Subclass Instance->method () (static methods can also be accessed by ordinary objects)
Note: The subclass instance->staticproperty (the static property of the parent class cannot be accessed through the subclass instance, there is an error: PHP Strict standards:accessing static Properties person::$ Country as non static in,php notice:undefined property:)

How the PHP subclass accesses the static method of the parent class