Description:
------------
https://3v4l.org/vMc1N contains the sample code where `&$this` as part of the callback invocation:

```
Hooks::run( 'foo', array( &$this, &$var ) );
```

causes a "Warning: Parameter 1 to {closure}() expected to be a reference, value given" on 7.1.0.

Running the provided sample code on 5.3.0 - 5.6.25, hhvm-3.10.0 - 3.12.0, 7.0.0 - 7.0.10 works as expected.

Re-declaring $this will pass on 7.1.0 and 5.3.0 - 5.6.25, hhvm-3.10.0 - 3.12.0, 7.0.0 - 7.0.10.

```
$foo = $this;
Hooks::run( 'foo', array( &$foo, &$var ) );
```

Test script:
---------------
https://3v4l.org/vMc1N