member variable and member function have the same name

See the chapter on Class Basic in the PHP manual:

$ins->isNew   // class member
$ins->isNew() // class method

$ins->isNew is the variable. $ins->isNew() is the function.

PHP is not a functional programming language where functions are also data. So $ins->isNew wouldn’t be ambiguous to either refer to the method isNew or the attribute isNew. $ins->isNew is always an attribute and $ins->isNew() a method call.