Description:
------------
Adding (string) cast to an exception object on output causes PHP to output the object identifier rather then executing __toString() and printing the defined text.

Removing the (string) cast on output makes the desired behaviour occur (print "Test 123").

Reproduce code:
---------------
<?php
class E extends Exception {
        public function __toString() {
                return "Test 123";
        }
}
try {
        throw new E();
} catch (E $e) {
        echo (string) $e;
}
?>

Expected result:
----------------
Test 123

Actual result:
--------------
Object id #1