Where do we use the object operator "->" in PHP?

When accessing a method or a property of an instantiated class

class SimpleClass
{
    // property declaration
    public $var = 'a default value';

    // method declaration
    public function displayVar() {
        echo $this->var;
    }
}

$a = new SimpleClass();
echo $a->var;
$a->displayVar();

PHP has two object operators.

The first, ->, is used when you want to call a method on an instance or access an instance property.

The second, ::, is used when you want to call a static method, access a static variable, or call a parent class's version of a method within a child class.