binary safe session persistence

[dnsl48]

FIX AWS SDK PHP DynamoDb StandardSessionConnection handles serialized sessions as strings, which is not binary safe

fixes #32

[dnsl48]

ready for a review

[chillu]

Works as advertised :) Was particularly interested in the transition of existing sessions once the new functionality is used. Tested with DynamoDB Local, see #34.

Add the following code to PageController->init():

$this->getRequest()->getSession()->set('foo', 'bar');

Use master branch. Visit /?flush=1. Observe session being created with string values:

aws dynamodb scan --table-name mysession --endpoint-url http://localhost:8000
{
    "Count": 1, 
    "Items": [
        {
            "expires": {
                "N": "1562024548"
            }, 
            "data": {
                "S": "foo|s:3:\"bar\";HTTP_USER_AGENT|s:121:\"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/75.0.3770.100 Safari/537.36\";"
            }, 
            "id": {
                "S": "PHPSESSID_7r6bcvrbb1cu8anch8img3lerp"
            }
        }
    ], 
    "ScannedCount": 1, 
    "ConsumedCapacity": null
}

Switch to PR branch. Visit /?flush=1 (in same browser session). Observe session data in DynamoDB hasn't changed.

Read out existing session value (in controller or elsewhere):

var_dump($this->getRequest()->getSession()->get('foo'));die();

Change the PageController->init() to a different session value:

$this->getRequest()->getSession()->set('foo', 'baz');

Visit /?flush=1. Observe session data changed to binary:

{
    "Count": 1, 
    "Items": [
        {
            "expires": {
                "N": "1562024689"
            }, 
            "data": {
                "B": "Zm9vfHM6MzoiYmF6IjtIVFRQX1VTRVJfQUdFTlR8czoxMjE6Ik1vemlsbGEvNS4wIChNYWNpbnRvc2g7IEludGVsIE1hYyBPUyBYIDEwXzE0XzUpIEFwcGxlV2ViS2l0LzUzNy4zNiAoS0hUTUwsIGxpa2UgR2Vja28pIENocm9tZS83NS4wLjM3NzAuMTAwIFNhZmFyaS81MzcuMzYiOw=="
            }, 
            "id": {
                "S": "PHPSESSID_7r6bcvrbb1cu8anch8img3lerp"
            }
        }
    ], 
    "ScannedCount": 1, 
    "ConsumedCapacity": null
}

Read out session value, observe new value:

var_dump($this->getRequest()->getSession()->get('foo'));die();