class - PHP Classes: when to use :: vs. ->?

Question

I understand that there are two ways to access a PHP class - "::" and "->". Sometime one seems to work for me, while the other doesn't, and I don't understand why.

What are the benefits of each, and what is the right situation to use either?

Answer 1

Simply put, :: is for class-level properties, and -> is for object-level properties.

If the property belongs to the class, use ::

If the property belongs to an instance of the class, use ->

class Tester
{
  public $foo;
  const BLAH;

  public static function bar(){}
}

$t = new Tester;
$t->foo;
Tester::bar();
Tester::BLAH;