# Zend_Service_WindowsAzure_Storage_Blob

Blob Storage stores sets of binary data. Blob storage offers the following three resources: the storage account, containers, and blobs. Within your storage account, containers provide a way to organize sets of blobs within your storage account.

Blob Storage is offered by Windows Azure as a REST API which is wrapped by the Zend_Service_WindowsAzure_Storage_Blob class in order to provide a native PHP interface to the storage account.

## API Examples

This topic lists some examples of using the Zend_Service_WindowsAzure_Storage_Blob class. Other features are available in the download package, as well as a detailed API documentation of those features.

### Creating a storage container

Using the following code, a blob storage container can be created on development storage.

Creating a storage container

    $storageClient = new Zend_Service_WindowsAzure_Storage_Blob();
    $result = $storageClient->createContainer('testcontainer');

    echo 'Container name is: ' . $result->Name;

### Deleting a storage container

Using the following code, a blob storage container can be removed from development storage.

Deleting a storage container

    $storageClient = new Zend_Service_WindowsAzure_Storage_Blob();
    $storageClient->deleteContainer('testcontainer');

### Storing a blob

Using the following code, a blob can be uploaded to a blob storage container on development storage. Note that the container has already been created before.

Storing a blob

    $storageClient = new Zend_Service_WindowsAzure_Storage_Blob();

    // upload /home/maarten/example.txt to Azure
    $result = $storageClient->putBlob(
        'testcontainer', 'example.txt', '/home/maarten/example.txt'
    );

    echo 'Blob name is: ' . $result->Name;

### Copying a blob

Using the following code, a blob can be copied from inside the storage account. The advantage of using this method is that the copy operation occurs in the Azure cloud and does not involve downloading the blob. Note that the container has already been created before.

Copying a blob

    $storageClient = new Zend_Service_WindowsAzure_Storage_Blob();

    // copy example.txt to example2.txt
    $result = $storageClient->copyBlob(
        'testcontainer', 'example.txt', 'testcontainer', 'example2.txt'
    );

    echo 'Copied blob name is: ' . $result->Name;

### Downloading a blob

Using the following code, a blob can be downloaded from a blob storage container on development storage. Note that the container has already been created before and a blob has been uploaded.

Downloading a blob

    $storageClient = new Zend_Service_WindowsAzure_Storage_Blob();

    // download file to /home/maarten/example.txt
    $storageClient->getBlob(
        'testcontainer', 'example.txt', '/home/maarten/example.txt'
    );

### Making a blob publicly available

By default, blob storage containers on Windows Azure are protected from public viewing. If any user on the Internet should have access to a blob container, its ACL can be set to public. Note that this applies to a complete container and not to a single blob!

Using the following code, blob storage container ACL can be set on development storage. Note that the container has already been created before.

Making a blob publicly available

    $storageClient = new Zend_Service_WindowsAzure_Storage_Blob();

    // make container publicly available (enumerate all blobs and read blob data)
    $storageClient->setContainerAcl('testcontainer', Zend_Service_WindowsAzure_Storage_Blob::ACL_PUBLIC_CONTAINER);

## Root container

Windows Azure Blob Storage provides support to work with a "root container". This means that a blob can be stored in the root of your storage account, i.e. `http://myaccount.blob.core.windows.net/somefile.txt`.

In order to work with the root container, it should first be created using the createContainer() method, naming the container `$root`. All other operations on the root container should be issued with the container name set to `$root`.

## Blob storage stream wrapper

The Windows Azure SDK for PHP provides support for registering a blob storage client as a PHP file stream wrapper. The blob storage stream wrapper provides support for using regular file operations on Windows Azure Blob Storage. For example, one can open a file from Windows Azure Blob Storage with the fopen() function:

Example usage of blob storage stream wrapper

    $fileHandle = fopen('azure://mycontainer/myfile.txt', 'r');

    // ...

    fclose($fileHandle);

In order to do this, the Windows Azure SDK for PHP blob storage client must be registered as a stream wrapper. This can be done by calling the registerStreamWrapper() method:

Registering the blob storage stream wrapper

    $storageClient = new Zend_Service_WindowsAzure_Storage_Blob();

    // registers azure:// on this storage client
    $storageClient->registerStreamWrapper();

    // or:

    // regiters blob:// on this storage client
    $storageClient->registerStreamWrapper('blob://');

To unregister the stream wrapper, the unregisterStreamWrapper() method can be used.

## Shared Access Signature

Windows Azure Bob Storage provides a feature called "Shared Access Signatures". By default, there is only one level of authorization possible in Windows Azure Blob Storage: either a container is private or it is public. Shared Access Signatures provide a more granular method of authorization: read, write, delete and list permissions can be assigned on a container or a blob and given to a specific client using an URL-based model.

An example would be the following signature:

    http://phpstorage.blob.core.windows.net/phpazuretestshared1?st=2009-08-17T09%3A06%3A17Z&se=2009-08-17T09%3A56%3A17Z&sr=c&sp=w&sig=hscQ7Su1nqd91OfMTwTkxabhJSaspx%2BD%2Fz8UqZAgn9s%3D

The above signature gives write access to the "phpazuretestshared1" container of the "phpstorage" account.

### Generating a Shared Access Signature

When you are the owner of a Windows Azure Bob Storage account, you can create and distribute a shared access key for any type of resource in your account. To do this, the generateSharedAccessUrl() method of the Zend_Service_WindowsAzure_Storage_Blob storage client can be used.

The following example code will generate a Shared Access Signature for write access in a container named "container1", within a timeframe of 3000 seconds.

Generating a Shared Access Signature for a container

    $storageClient   = new Zend_Service_WindowsAzure_Storage_Blob();
    $sharedAccessUrl = $storageClient->generateSharedAccessUrl(
        'container1',
        '',
        'c',
        'w',
        $storageClient ->isoDate(time() - 500),
        $storageClient ->isoDate(time() + 3000)
    );

The following example code will generate a Shared Access Signature for read access in a blob named `test.txt` in a container named "container1" within a time frame of 3000 seconds.

Generating a Shared Access Signature for a blob

    $storageClient   = new Zend_Service_WindowsAzure_Storage_Blob();
    $sharedAccessUrl = $storageClient->generateSharedAccessUrl(
        'container1',
        'test.txt',
        'b',
        'r',
        $storageClient ->isoDate(time() - 500),
        $storageClient ->isoDate(time() + 3000)
    );

### Working with Shared Access Signatures from others

When you receive a Shared Access Signature from someone else, you can use the Windows Azure SDK for PHP to work with the addressed resource. For example, the following signature can be retrieved from the owner of a storage account:

    http://phpstorage.blob.core.windows.net/phpazuretestshared1?st=2009-08-17T09%3A06%3A17Z&se=2009-08-17T09%3A56%3A17Z&sr=c&sp=w&sig=hscQ7Su1nqd91OfMTwTkxabhJSaspx%2BD%2Fz8UqZAgn9s%3D

The above signature gives write access to the "phpazuretestshared1" "container" of the phpstorage account. Since the shared key for the account is not known, the Shared Access Signature can be used to work with the authorized resource.

Consuming a Shared Access Signature for a container

    $storageClient = new Zend_Service_WindowsAzure_Storage_Blob(
        'blob.core.windows.net', 'phpstorage', ''
    );
    $storageClient->setCredentials(
        new Zend_Service_WindowsAzure_Credentials_SharedAccessSignature()
    );
    $storageClient->getCredentials()->setPermissionSet(array(
        'http://phpstorage.blob.core.windows.net/phpazuretestshared1?st=2009-08-17T09%3A06%3A17Z&se=2009-08-17T09%3A56%3A17Z&sr=c&sp=w&sig=hscQ7Su1nqd91OfMTwTkxabhJSaspx%2BD%2Fz8UqZAgn9s%3D'
    ));
    $storageClient->putBlob(
        'phpazuretestshared1', 'NewBlob.txt', 'C:\Files\dataforazure.txt'
    );

Note that there was no explicit permission to write to a specific blob. Instead, the Windows Azure SDK for PHP determined that a permission was required to either write to that specific blob, or to write to its container. Since only a signature was available for the latter, the Windows Azure SDK for PHP chose those credentials to perform the request on Windows Azure blob storage.