Description:
------------
In a php_user_filter class the property $stream is not set to the current stream in PHP 7.0.13 (and 7.0.12, 7.0.8) while executing the method filter(). I tried the example script from
http://stackoverflow.com/questions/27103269/what-is-a-bucket-brigade

It does work in PHP 5.3.29.

Test script:
---------------
<?php
class append_filter extends php_user_filter {
    public $stream;
    function filter($in, $out, &$consumed, $closing) {
        while ($bucket = stream_bucket_make_writeable($in)) {
            $consumed += $bucket->datalen;
            stream_bucket_append($out, $bucket);
        }
        if ($closing) {
            $bucket = stream_bucket_new($this->stream, "FooBar \n");
            stream_bucket_append($out, $bucket);
        }
        return PSFS_PASS_ON;
    }
}
stream_filter_register("append", "append_filter");
$fin = fopen($argv[1], 'rb');
stream_filter_append($fin, 'append', STREAM_FILTER_READ);
stream_copy_to_stream($fin, fopen('out', 'wb'));


Expected result:
----------------
In PHP 5.3.29 the, on the command line given, input file is copied to the file 'out' and "FooBar \n" is append to the file 'out'.

Actual result:
--------------
In PHP 7 the given file is just copied (whit out append the string) and error messages like this are produced:

PHP Notice:  Undefined property: append_filter::$stream in test-filter.php on line 10
PHP Warning:  stream_bucket_new(): supplied argument is not a valid stream resource in test-filter.php on line 10
PHP Warning:  stream_bucket_append() expects parameter 2 to be object, boolean given in test-filter.php on line 11