PHP Function Stream_Filter_Append()

Streams are a powerful concept in PHP, and can be used for anything from file read/write processes to standard input/output processes. They’re like a conveyor belt of things that come to you one by one, rather than having to constantly do something yourself. There are a number of specific functions for performing various streams operations, and they’re used by many different plugins and extensions.

Amongst these, php function stream_filter_append() is a very useful function that allows you to apply filters to the stream. A filter is something that performs an operation on data as it’s being read or written. For example, you might want to change header information, or filter a stream for particular characters. Filters can be stacked onto streams, and the order of them is important when working with streams.

When you call stream_filter_append(), the new filter is added to the list of filters attached to the stream. By default, it will be attached to the read filter chain if the stream is opened for reading, and to the write filter chain if the stream is opened for writing. STREAM_FILTER_APPEND_READ, STREAM_FILTER_APPEND_WRITE, and STREAM_FILTER_ALL are alternative constants that can be passed to the function to override this behavior.

Just like with any other file or socket related function, there are a number of things that can cause an operation on a stream to fail. For example, a connection to a remote host may not be available, or an error within the stream itself might occur. Errors that affect a stream are typically reported as a warning level E_WARNING.

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stream_filter_append example

if (isset($context['ssl']['capture_peer_cert_chain']) && isset(($context = stream_context_get_options($this->context))['ssl']['peer_certificate_chain'])) {
            $this->info['peer_certificate_chain'] = $context['ssl']['peer_certificate_chain'];
        }

        stream_set_blocking($h, false);
        unset($this->context, $this->resolver);

        // Create dechunk buffers         if (isset($this->headers['content-length'])) {
            $this->remaining = (int) $this->headers['content-length'][0];
        } elseif ('chunked' === ($this->headers['transfer-encoding'][0] ?? null)) {
            stream_filter_append($this->buffer, 'dechunk', \STREAM_FILTER_WRITE);
            $this->remaining = -1;
        } else {
            $this->remaining = -2;
        }

        $this->multi->handlesActivity[$this->id] = [new FirstChunk()];

        if ('HEAD' === $context['http']['method'] || \in_array($this->info['http_code'], [204, 304], true)) {
            $this->multi->handlesActivity[$this->id][] = null;
            $this->multi->handlesActivity[$this->id][] = null;

            

class UnitTestCaseTest extends UnitTestCase {

  /** * Tests the dump() function in a test run in the same process. */
  public function testVarDumpSameProcess() {
    // Append the stream capturer to the STDOUT stream, so that we can test the     // dump() output and also prevent it from actually outputting in this     // particular test.     stream_filter_register("capture", StreamCapturer::class);
    stream_filter_append(STDOUT, "capture");

    // Dump some variables.     $object = (object) [
      'foo' => 'bar',
    ];
    dump($object);
    dump('banana');

    $this->assertStringContainsString('bar', StreamCapturer::$cache);
    $this->assertStringContainsString('banana', StreamCapturer::$cache);
  }

  
$this->assertCount(1, $test_deprecation_messages);
  }

  /** * Tests the dump() function provided by the var-dumper Symfony component. */
  public function testVarDump() {
    // Append the stream capturer to the STDOUT stream, so that we can test the     // dump() output and also prevent it from actually outputting in this     // particular test.     stream_filter_register("capture", StreamCapturer::class);
    stream_filter_append(STDOUT, "capture");

    // Dump some variables to check that dump() in test code produces output     // on the command line that is running the test.     $role = Role::load('authenticated');
    dump($role);
    dump($role->id());

    $this->assertStringContainsString('Drupal\user\Entity\Role', StreamCapturer::$cache);
    $this->assertStringContainsString('authenticated', StreamCapturer::$cache);

    // Visit a Drupal page with call to the dump() function to check that dump()
if (!\is_array(@stream_get_meta_data($body))) {
            throw new InvalidArgumentException(sprintf('Option "body" must be string, stream resource, iterable or callable, "%s" given.', get_debug_type($body)));
        }

        return $body;
    }

    private static function dechunk(string $body): string
    {
        $h = fopen('php://temp', 'w+');
        stream_filter_append($h, 'dechunk', \STREAM_FILTER_WRITE);
        fwrite($h, $body);
        $body = stream_get_contents($h, -1, 0);
        rewind($h);
        ftruncate($h, 0);

        if (fwrite($h, '-') && '' !== stream_get_contents($h, -1, 0)) {
            throw new TransportException('Request body has broken chunked encoding.');
        }

        return $body;
    }

    
/** @var StreamInterface */
    private $stream;

    public function __construct(StreamInterface $stream)
    {
        $resource = StreamWrapper::getResource($stream);
        // Specify window=15+32, so zlib will use header detection to both gzip (with header) and zlib data         // See http://www.zlib.net/manual.html#Advanced definition of inflateInit2         // "Add 32 to windowBits to enable zlib and gzip decoding with automatic header detection"         // Default window size is 15.         stream_filter_append($resource, 'zlib.inflate', STREAM_FILTER_READ, ['window' => 15 + 32]);
        $this->stream = $stream->isSeekable() ? new Stream($resource) : new NoSeekStream(new Stream($resource));
    }
}
/** * @author Fabien Potencier <fabien@symfony.com> */
final class Base64ContentEncoder extends Base64Encoder implements ContentEncoderInterface
{
    public function encodeByteStream($stream, int $maxLineLength = 0): iterable
    {
        if (!\is_resource($stream)) {
            throw new \TypeError(sprintf('Method "%s" takes a stream as a first argument.', __METHOD__));
        }

        $filter = stream_filter_append($stream, 'convert.base64-encode', \STREAM_FILTER_READ, [
            'line-length' => 0 >= $maxLineLength || 76 < $maxLineLength ? 76 : $maxLineLength,
            'line-break-chars' => "\r\n",
        ]);
        if (!\is_resource($filter)) {
            throw new RuntimeException('Unable to set the base64 content encoder to the filter.');
        }

        while (!feof($stream)) {
            yield fread($stream, 16372);
        }
        stream_filter_remove($filter);
    }
/** * @author Fabien Potencier <fabien@symfony.com> */
final class Base64ContentEncoder extends Base64Encoder implements ContentEncoderInterface
{
    public function encodeByteStream($stream, int $maxLineLength = 0): iterable
    {
        if (!\is_resource($stream)) {
            throw new \TypeError(sprintf('Method "%s" takes a stream as a first argument.', __METHOD__));
        }

        $filter = stream_filter_append($stream, 'convert.base64-encode', \STREAM_FILTER_READ, [
            'line-length' => 0 >= $maxLineLength || 76 < $maxLineLength ? 76 : $maxLineLength,
            'line-break-chars' => "\r\n",
        ]);
        if (!\is_resource($filter)) {
            throw new RuntimeException('Unable to set the base64 content encoder to the filter.');
        }

        while (!feof($stream)) {
            yield fread($stream, 16372);
        }
        stream_filter_remove($filter);
    }

  }

  /** * Tests the dump() function provided by the var-dumper Symfony component. */
  public function testVarDump() {
    // Append the stream capturer to the STDOUT stream, so that we can test the     // dump() output and also prevent it from actually outputting in this     // particular test.     stream_filter_register("capture", StreamCapturer::class);
    stream_filter_append(STDOUT, "capture");

    // Dump some variables.     $this->enableModules(['system', 'user']);
    $role = Role::create(['id' => 'test_role', 'label' => 'Test role']);
    dump($role);
    dump($role->id());

    $this->assertStringContainsString('Drupal\user\Entity\Role', StreamCapturer::$cache);
    $this->assertStringContainsString('test_role', StreamCapturer::$cache);
  }

  

    public function getEncodedStream()
    {
        if (!$this->_isStream) {
            throw new Zend_Mime_Exception('Attempt to get a stream from a string part');
        }

        //stream_filter_remove(); // ??? is that right?         switch ($this->encoding) {
            case Zend_Mime::ENCODING_QUOTEDPRINTABLE:
                $filter = stream_filter_append(
                    $this->_content,
                    'convert.quoted-printable-encode',
                    STREAM_FILTER_READ,
                    array(
                        'line-length'      => 76,
                        'line-break-chars' => Zend_Mime::LINEEND
                    )
                );
                if (!is_resource($filter)) {
                    throw new Zend_Mime_Exception('Failed to append quoted-printable filter');
                }
                

        if (! static::$registered) {
            static::$registered = stream_filter_register('CITestStreamFilter', self::class); // @codeCoverageIgnore         }

        static::$buffer = '';
    }

    public static function addErrorFilter(): void
    {
        self::removeFilter(self::$err);
        self::$err = stream_filter_append(STDERR, 'CITestStreamFilter');
    }

    public static function addOutputFilter(): void
    {
        self::removeFilter(self::$out);
        self::$out = stream_filter_append(STDOUT, 'CITestStreamFilter');
    }

    public static function removeErrorFilter(): void
    {
        self::removeFilter(self::$err);
    }
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