invalid-vars.php

<?php

class Foo {
	public function __construct() {
		$this->prop = 'a';
		$this->{'contains-minus'} = 'b';
		$this->{''} = 'c';
	}
}

$obj = new Foo();

var_dump($obj->prop); // 'a'
var_dump($obj->contains-minus); // int(0) - notice: undefined property Foo::$contains, warning: undefined constant minus, assumed 'minus'
var_dump($obj->{'contains-minus'}); // 'b'
// var_dump($obj->); // Syntax error, unexpected ')'
// var_dump($obj->''); // Syntax error, unexpected ''''
var_dump($obj->{''}); // 'c'