PHP:: The difference between the self $this operator

When accessing member variables or methods in a PHP class,

If the referenced variable or method is declared as const (defining a constant) or static (declaring static), then the operator must be used ::,

Conversely , if the referenced variable or method is not declared as const or static , then you must use the operator ---.

Const or Static	Use::
Not const or static	With

In addition, if you access a const or static variable or method from within a class, you must use self -referencing,

Conversely , if accessing from within a class is not a const or static variable or method, you must use a self-referencing $this .

Const or Static	With self
Not const or static	With $this

PHP:: The difference between the self $this operator