========================
Amazon S3 Stream Wrapper
========================

Introduction
------------

The Amazon S3 stream wrapper allows you to store and retrieve data from Amazon S3 using built-in PHP functions like
``file_get_contents``, ``fopen``, ``copy``, ``rename``, ``unlink``, ``mkdir``, ``rmdir``, etc.

You need to register the Amazon S3 stream wrapper in order to use it:

.. code-block:: php

    // Register the stream wrapper from an S3Client object
    $client->registerStreamWrapper();

This allows you to access buckets and objects stored in Amazon S3 using the ``s3://`` protocol. The "s3" stream wrapper
accepts strings that contain a bucket name followed by a forward slash and an optional object key or prefix:
``s3://<bucket>[/<key-or-prefix>]``.

Downloading data
----------------

You can grab the contents of an object using ``file_get_contents``. Be careful with this function though; it loads the
entire contents of the object into memory.

.. code-block:: php

    // Download the body of the "key" object in the "bucket" bucket
    $data = file_get_contents('s3://bucket/key');

Use ``fopen()`` when working with larger files or if you need to stream data from Amazon S3.

.. code-block:: php

    // Open a stream in read-only mode
    if ($stream = fopen('s3://bucket/key', 'r')) {
        // While the stream is still open
        while (!feof($stream)) {
            // Read 1024 bytes from the stream
            echo fread($stream, 1024);
        }
        // Be sure to close the stream resource when you're done with it
        fclose($stream);
    }

Opening Seekable streams
~~~~~~~~~~~~~~~~~~~~~~~~

Streams opened in "r" mode only allow data to be read from the stream, and are not seekable by default. This is so that
data can be downloaded from Amazon S3 in a truly streaming manner where previously read bytes do not need to be
buffered into memory. If you need a stream to be seekable, you can pass ``seekable`` into the `stream context
options <http://www.php.net/manual/en/function.stream-context-create.php>`_ of a function.

.. code-block:: php

    $context = stream_context_create(array(
        's3' => array(
            'seekable' => true
        )
    ));

    if ($stream = fopen('s3://bucket/key', 'r', false, $context)) {
        // Read bytes from the stream
        fread($stream, 1024);
        // Seek back to the beginning of the stream
        fseek($steam, 0);
        // Read the same bytes that were previously read
        fread($stream, 1024);
        fclose($stream);
    }

Opening seekable streams allows you to seek only to bytes that were previously read. You cannot skip ahead to bytes
that have not yet been read from the remote server. In order to allow previously read data to recalled, data is
buffered in a PHP temp stream using Guzzle's
`CachingEntityBody <https://github.com/guzzle/guzzle/blob/master/src/Guzzle/Http/CachingEntityBody.php>`_ decorator.
When the amount of cached data exceed 2MB, the data in the temp stream will transfer from memory to disk. Keep this in
mind when downloading large files from Amazon S3 using the ``seekable`` stream context setting.

Uploading data
--------------

Data can be uploaded to Amazon S3 using ``file_put_contents()``.

.. code-block:: php

    file_put_contents('s3://bucket/key', 'Hello!');

You can upload larger files by streaming data using ``fopen()`` and a "w", "x", or "a" stream access mode. The Amazon
S3 stream wrapper does **not** support simultaneous read and write streams (e.g. "r+", "w+", etc). This is because the
HTTP protocol does not allow simultaneous reading and writing.

.. code-block:: php

    $stream = fopen('s3://bucket/key', 'w');
    fwrite($stream, 'Hello!');
    fclose($stream);

.. note::

    Because Amazon S3 requires a Content-Length header to be specified before the payload of a request is sent, the
    data to be uploaded in a PutObject operation is internally buffered using a PHP temp stream until the stream is
    flushed or closed.

fopen modes
-----------

PHP's `fopen() <http://php.net/manual/en/function.fopen.php>`_ function requires that a ``$mode`` option is specified.
The mode option specifies whether or not data can be read or written to a stream and if the file must exist when
opening a stream. The Amazon S3 stream wrapper supports the following modes:

= ======================================================================================================================
r A read only stream where the file must already exist.
w A write only stream. If the file already exists it will be overwritten.
a A write only stream. If the file already exists, it will be downloaded to a temporary stream and any writes to
  the stream will be appended to any previously uploaded data.
x A write only stream. An error is raised if the file does not already exist.
= ======================================================================================================================

Other object functions
----------------------

Stream wrappers allow many different built-in PHP functions to work with a custom system like Amazon S3. Here are some
of the functions that the Amazon S3 stream wrapper allows you to perform with objects stored in Amazon S3.

=============== ========================================================================================================
unlink()        Delete an object from a bucket.

                .. code-block:: php

                    // Delete an object from a bucket
                    unlink('s3://bucket/key');

                You can pass in any options available to the ``DeleteObject`` operation to modify how the object is
                deleted (e.g. specifying a specific object version).

                .. code-block:: php

                    // Delete a specific version of an object from a bucket
                    unlink('s3://bucket/key', stream_context_create(array(
                        's3' => array('VersionId' => '123')
                    ));

filesize()      Get the size of an object.

                .. code-block:: php

                    // Get the Content-Length of an object
                    $size = filesize('s3://bucket/key');

is_file()       Checks if a URL is a file.

                .. code-block:: php

                    if (is_file('s3://bucket/key')) {
                        echo 'It is a file!';
                    }

file_exists()   Checks if an object exists.

                .. code-block:: php

                    if (file_exists('s3://bucket/key')) {
                        echo 'It exists!';
                    }

filetype()      Checks if a URL maps to a file or bucket (dir).
file()          Load the contents of an object in an array of lines. You can pass in any options available to the
                ``GetObject`` operation to modify how the file is downloaded.
filemtime()     Get the last modified date of an object.
rename()        Rename an object by copying the object then deleting the original. You can pass in options available to
                the ``CopyObject`` and ``DeleteObject`` operations to the stream context parameters to modify how the
                object is copied and deleted.
copy()          Copy an object from one location to another. You can pass options available to the ``CopyObject``
                operation into the stream context options to modify how the object is copied.

                .. code-block:: php

                    // Copy a file on Amazon S3 to another bucket
                    copy('s3://bucket/key', 's3://other_bucket/key');

=============== ========================================================================================================

Working with buckets
--------------------

You can modify and browse Amazon S3 buckets similar to how PHP allows the modification and traversal of directories on
your filesystem.

Here's an example of creating a bucket:

.. code-block:: php

    mkdir('s3://bucket');

You can pass in stream context options to the ``mkdir()`` method to modify how the bucket is created using the
parameters available to the
`CreateBucket <http://docs.aws.amazon.com/aws-sdk-php/v2/api/class-Aws.S3.S3Client.html#_createBucket>`_ operation.

.. code-block:: php

    // Create a bucket in the EU region
    mkdir('s3://bucket', '0777', false, stream_context_create(array(
        's3' => array(
            'LocationConstraint' => 'eu-west-1'
        )
    )));

You can delete buckets using the ``rmdir()`` function.

.. code-block:: php

    // Delete a bucket
    rmdir('s3://bucket');

.. note::

    A bucket can only be deleted if it is empty.

Listing the contents of a bucket
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The `opendir() <http://www.php.net/manual/en/function.opendir.php>`_,
`readdir() <http://www.php.net/manual/en/function.readdir.php>`_,
`rewinddir() <http://www.php.net/manual/en/function.rewinddir.php>`_, and
`closedir() <http://php.net/manual/en/function.closedir.php>`_ PHP functions can be used with the Amazon S3 stream
wrapper to traverse the contents of a bucket. You can pass in parameters available to the
`ListObjects <http://docs.aws.amazon.com/aws-sdk-php/v2/api/class-Aws.S3.S3Client.html#_listObjects>`_ operation as
custom stream context options to the ``opendir()`` function to modify how objects are listed.

.. code-block:: php

    $dir = "s3://bucket/";

    if (is_dir($dir) && ($dh = opendir($dir))) {
        while (($file = readdir($dh)) !== false) {
            echo "filename: {$file} : filetype: " . filetype($dir . $file) . "\n";
        }
        closedir($dh);
    }

You can recursively list each object and prefix in a bucket using PHP's
`RecursiveDirectoryIterator <http://php.net/manual/en/class.recursivedirectoryiterator.php>`_.

.. code-block:: php

    $dir = 's3://bucket';
    $iterator = new RecursiveIteratorIterator(new RecursiveDirectoryIterator($dir));

    foreach ($iterator as $file) {
        echo $file->getType() . ': ' . $file . "\n";
    }

Another easy way to list the contents of the bucket is using the
`Symfony2 Finder component <http://symfony.com/doc/master/components/finder.html>`_.

.. code-block:: php

    <?php

    require 'vendor/autoload.php';

    use Symfony\Component\Finder\Finder;

    $aws = Aws\Common\Aws::factory('/path/to/config.json');
    $s3 = $aws->get('s3')->registerStreamWrapper();

    $finder = new Finder();

    // Get all files and folders (key prefixes) from "bucket" that are less than 100k
    // and have been updated in the last year
    $finder->in('s3://bucket')
        ->size('< 100K')
        ->date('since 1 year ago');

    foreach ($finder as $file) {
        echo $file->getType() . ": {$file}\n";
    }
