I have confirmed stream_select() behave differently on 5.3.29 (tested on OS X).

/******** TEST CODE ********/
$read = $except = null;
$write = array("test" => fopen("php://stdout", "w"));

var_dump($write);
stream_select($read, $write, $except, 0);
var_dump($write);

/******** PHP 5.6.4 ********/
array(1) {
  ["test"]=>
  resource(5) of type (stream)
}
array(1) {
  ["test"]=>
  resource(5) of type (stream)
}

/******** PHP 5.3.29 ********/
array(1) {
  ["test"]=>
  resource(5) of type (stream)
}
array(1) {
  [0]=>
  resource(5) of type (stream)
}


Example of code which conforms to documentation of stream_select() but fails on 5.6.4:

$read = $except = null;
$write = array("test" => fopen("php://stdout", "w"));

stream_select($read, $write, $except, 0);
for($i = 0; $i < count($write); $i++) {
 var_dump($write[$i]); //"resource(n) of type (stream)" on 5.3.29, NULL on 5.6.4
}

A bit late to document this, though.