The difference between ::, ->, self and $this operators in PHP

When accessing member variables or methods in a PHP class, if the referenced variable or method is declared as const (defining constant) or static (declaring static), then you must use the operator::,

and vice versa. If the referenced variable or method is not declared const or static, the operator -> must be used.

In addition, if you access a const or static variable or method from inside the class, you must use self-reference,

On the contrary, if you access a non-const or static variable or method from inside the class, then Must use self-referential $this.

The above introduces the differences between ::, ->, self, and $this operators in PHP, including the relevant content. I hope it will be helpful to friends who are interested in PHP tutorials.