add test for bug

Zend/tests/bug71359.phpt

@@ -0,0 +1,61 @@
+--TEST--
+Bug #71359: Null coalescing operator and magic
+--FILE--
+<?php
+class AA {
+    private $data = [];
+    public function __isset($name) {
+        echo "__isset($name)\n";
+        return array_key_exists($name, $this->data);
+    }
+    public function &__get($name) {
+        echo "__get($name)\n";
+        if (!array_key_exists($name, $this->data)) {
+            throw new Exception('Unknown offset');
+        }
+        return $this->data[$name];
+    }
+    public function __set($name, $value) {
+        echo "__set($name)\n";
+        $this->data[$name] = $value;
+    }
+    public function __unset($name) {
+        echo "__unset($name)\n";
+        unset($this->data[$name]);
+    }
+}
+
+$aa = new AA;
+var_dump(isset($aa->zero->one->two));
+var_dump(isset($aa->zero->foo));
+var_dump($aa->zero ?? 42);
+var_dump($aa->zero->one->two ?? 42);
+$aa->zero = new AA;
+$aa->zero->one = new AA;
+var_dump(isset($aa->zero->one->two));
+var_dump($aa->zero->one->two ?? 42);
+?>
+--EXPECT--
+__isset(zero)
+bool(false)
+__isset(zero)
+bool(false)
+__isset(zero)
+int(42)
+__isset(zero)
+int(42)
+__set(zero)
+__get(zero)
+__set(one)
+__isset(zero)
+__get(zero)
+__isset(one)
+__get(one)
+__isset(two)
+bool(false)
+__isset(zero)
+__get(zero)
+__isset(one)
+__get(one)
+__isset(two)
+int(42)