gem-hunter

Event-driven readable and writable streams for non-blocking I/O in ReactPHP.

Development version: This branch contains the code for the upcoming v3 release. For the code of the current stable v1 release, check out the 1.x branch.

The upcoming v3 release will be the way forward for this package. However, we will still actively support v1 for those not yet on the latest version. See also installation instructions for more details.

In order to make the EventLoop easier to use, this component introduces the powerful concept of "streams". Streams allow you to efficiently process huge amounts of data (such as a multi Gigabyte file download) in small chunks without having to store everything in memory at once. They are very similar to the streams found in PHP itself, but have an interface more suited for async, non-blocking I/O.

Table of contents

• Stream usage
  • ReadableStreamInterface
    • data event
    • end event
    • error event
    • close event
    • isReadable()
    • pause()
    • resume()
    • pipe()
    • close()
  • WritableStreamInterface
    • drain event
    • pipe event
    • error event
    • close event
    • isWritable()
    • write()
    • end()
    • close()
  • DuplexStreamInterface
• Creating streams
  • ReadableResourceStream
  • WritableResourceStream
  • DuplexResourceStream
  • ThroughStream
  • CompositeStream
• Usage
• Install
• Tests
• License
• More

ReactPHP uses the concept of "streams" throughout its ecosystem to provide a consistent higher-level abstraction for processing streams of arbitrary data contents and size. While a stream itself is a quite low-level concept, it can be used as a powerful abstraction to build higher-level components and protocols on top.

If you're new to this concept, it helps to think of them as a water pipe: You can consume water from a source or you can produce water and forward (pipe) it to any destination (sink).

Similarly, streams can either be

• readable (such as STDIN terminal input) or
• writable (such as STDOUT terminal output) or
• duplex (both readable and writable, such as a TCP/IP connection)

Accordingly, this package defines the following three interfaces

• ReadableStreamInterface
• WritableStreamInterface
• DuplexStreamInterface

The ReadableStreamInterface is responsible for providing an interface for read-only streams and the readable side of duplex streams.

Besides defining a few methods, this interface also implements the EventEmitterInterface which allows you to react to certain events.

The event callback functions MUST be a valid callable that obeys strict parameter definitions and MUST accept event parameters exactly as documented. The event callback functions MUST NOT throw an Exception. The return value of the event callback functions will be ignored and has no effect, so for performance reasons you're recommended to not return any excessive data structures.

Every implementation of this interface MUST follow these event semantics in order to be considered a well-behaving stream.

Note that higher-level implementations of this interface may choose to define additional events with dedicated semantics not defined as part of this low-level stream specification. Conformance with these event semantics is out of scope for this interface, so you may also have to refer to the documentation of such a higher-level implementation.

The data event will be emitted whenever some data was read/received from this source stream. The event receives a single mixed argument for incoming data.

$stream->on('data', function (mixed $data): void {
    echo $data;
});

This event MAY be emitted any number of times, which may be zero times if this stream does not send any data at all. It SHOULD not be emitted after an end or close event.

The given $data argument may be of mixed type, but it's usually recommended it SHOULD be a string value or MAY use a type that allows representation as a string for maximum compatibility.

Many common streams (such as a TCP/IP connection or a file-based stream) will emit the raw (binary) payload data that is received over the wire as chunks of string values.

Due to the stream-based nature of this, the sender may send any number of chunks with varying sizes. There are no guarantees that these chunks will be received with the exact same framing the sender intended to send. In other words, many lower-level protocols (such as TCP/IP) transfer the data in chunks that may be anywhere between single-byte values to several dozens of kilobytes. You may want to apply a higher-level protocol to these low-level data chunks in order to achieve proper message framing.

The end event will be emitted once the source stream has successfully reached the end of the stream (EOF).

$stream->on('end', function (): void {
    echo 'END';
});

This event SHOULD be emitted once or never at all, depending on whether a successful end was detected. It SHOULD NOT be emitted after a previous end or close event. It MUST NOT be emitted if the stream closes due to a non-successful end, such as after a previous error event.

After the stream is ended, it MUST switch to non-readable mode, see also isReadable().

This event will only be emitted if the end was reached successfully, not if the stream was interrupted by an unrecoverable error or explicitly closed. Not all streams know this concept of a "successful end". Many use-cases involve detecting when the stream closes (terminates) instead, in this case you should use the close event. After the stream emits an end event, it SHOULD usually be followed by a close event.

Many common streams (such as a TCP/IP connection or a file-based stream) will emit this event if either the remote side closes the connection or a file handle was successfully read until reaching its end (EOF).

Note that this event should not be confused with the end() method. This event defines a successful end reading from a source stream, while the end() method defines writing a successful end to a destination stream.

The error event will be emitted once a fatal error occurs, usually while trying to read from this stream. The event receives a single Exception argument for the error instance.

$server->on('error', function (Exception $e): void {
    echo 'Error: ' . $e->getMessage() . PHP_EOL;
});

This event SHOULD be emitted once the stream detects a fatal error, such as a fatal transmission error or after an unexpected data or premature end event. It SHOULD NOT be emitted after a previous error, end or close event. It MUST NOT be emitted if this is not a fatal error condition, such as a temporary network issue that did not cause any data to be lost.

After the stream errors, it MUST close the stream and SHOULD thus be followed by a close event and then switch to non-readable mode, see also close() and isReadable().

Many common streams (such as a TCP/IP connection or a file-based stream) only deal with data transmission and do not make assumption about data boundaries (such as unexpected data or premature end events). In other words, many lower-level protocols (such as TCP/IP) may choose to only emit this for a fatal transmission error once and will then close (terminate) the stream in response.

If this stream is a DuplexStreamInterface, you should also notice how the writable side of the stream also implements an error event. In other words, an error may occur while either reading or writing the stream which should result in the same error processing.

The close event will be emitted once the stream closes (terminates).

$stream->on('close', function (): void {
    echo 'CLOSED';
});

This event SHOULD be emitted once or never at all, depending on whether the stream ever terminates. It SHOULD NOT be emitted after a previous close event.

After the stream is closed, it MUST switch to non-readable mode, see also isReadable().

Unlike the end event, this event SHOULD be emitted whenever the stream closes, irrespective of whether this happens implicitly due to an unrecoverable error or explicitly when either side closes the stream. If you only want to detect a successful end, you should use the end event instead.

Many common streams (such as a TCP/IP connection or a file-based stream) will likely choose to emit this event after reading a successful end event or after a fatal transmission error event.

If this stream is a DuplexStreamInterface, you should also notice how the writable side of the stream also implements a close event. In other words, after receiving this event, the stream MUST switch into non-writable AND non-readable mode, see also isWritable(). Note that this event should not be confused with the end event.

The isReadable(): bool method can be used to check whether this stream is in a readable state (not closed already).

This method can be used to check if the stream still accepts incoming data events or if it is ended or closed already. Once the stream is non-readable, no further data or end events SHOULD be emitted.

assert($stream->isReadable() === false);

$stream->on('data', assertNeverCalled());
$stream->on('end', assertNeverCalled());

A successfully opened stream always MUST start in readable mode.

Once the stream ends or closes, it MUST switch to non-readable mode. This can happen any time, explicitly through close() or implicitly due to a remote close or an unrecoverable transmission error. Once a stream has switched to non-readable mode, it MUST NOT transition back to readable mode.

If this stream is a DuplexStreamInterface, you should also notice how the writable side of the stream also implements an isWritable() method. Unless this is a half-open duplex stream, they SHOULD usually have the same return value.

The pause(): void method can be used to pause reading incoming data events.

Removes the data source file descriptor from the event loop. This allows you to throttle incoming data.

Unless otherwise noted, a successfully opened stream SHOULD NOT start in paused state.

Once the stream is paused, no futher data or end events SHOULD be emitted.

$stream->pause();

$stream->on('data', assertShouldNeverCalled());
$stream->on('end', assertShouldNeverCalled());

This method is advisory-only, though generally not recommended, the stream MAY continue emitting data events.

You can continue processing events by calling resume() again.

Note that both methods can be called any number of times, in particular calling pause() more than once SHOULD NOT have any effect.

See also resume().

The resume(): void method can be used to resume reading incoming data events.

Re-attach the data source after a previous pause().

$stream->pause();

Loop::addTimer(1.0, function () use ($stream): void {
    $stream->resume();
});

Note that both methods can be called any number of times, in particular calling resume() without a prior pause() SHOULD NOT have any effect.

See also pause().

The pipe(WritableStreamInterface $dest, array $options = []): WritableStreamInterface method can be used to pipe all the data from this readable source into the given writable destination.

Automatically sends all incoming data to the destination. Automatically throttles the source based on what the destination can handle.

$source->pipe($dest);

Similarly, you can also pipe an instance implementing DuplexStreamInterface into itself in order to write back all the data that is received. This may be a useful feature for a TCP/IP echo service:

$connection->pipe($connection);

This method returns the destination stream as-is, which can be used to set up chains of piped streams:

$source->pipe($decodeGzip)->pipe($filterBadWords)->pipe($dest);

By default, this will call end() on the destination stream once the source stream emits an end event. This can be disabled like this:

$source->pipe($dest, ['end' => false]);

Note that this only applies to the end event. If an error or explicit close event happens on the source stream, you'll have to manually close the destination stream:

$source->pipe($dest);
$source->on('close', function () use ($dest): void {
    $dest->end('BYE!');
});

If the source stream is not readable (closed state), then this is a NO-OP.

$source->close();
$source->pipe($dest); // NO-OP

If the destinantion stream is not writable (closed state), then this will simply throttle (pause) the source stream:

$dest->close();
$source->pipe($dest); // calls $source->pause()

Similarly, if the destination stream is closed while the pipe is still active, it will also throttle (pause) the source stream:

$source->pipe($dest);
$dest->close(); // calls $source->pause()

Once the pipe is set up successfully, the destination stream MUST emit a pipe event with this source stream an event argument.

The close(): void method can be used to close the stream (forcefully).

This method can be used to (forcefully) close the stream.

$stream->close();

Once the stream is closed, it SHOULD emit a close event. Note that this event SHOULD NOT be emitted more than once, in particular if this method is called multiple times.

After calling this method, the stream MUST switch into a non-readable mode, see also isReadable(). This means that no further data or end events SHOULD be emitted.

$stream->close();
assert($stream->isReadable() === false);

$stream->on('data', assertNeverCalled());
$stream->on('end', assertNeverCalled());

If this stream is a DuplexStreamInterface, you should also notice how the writable side of the stream also implements a close() method. In other words, after calling this method, the stream MUST switch into non-writable AND non-readable mode, see also isWritable(). Note that this method should not be confused with the end() method.

The WritableStreamInterface is responsible for providing an interface for write-only streams and the writable side of duplex streams.

Besides defining a few methods, this interface also implements the EventEmitterInterface which allows you to react to certain events.

The event callback functions MUST be a valid callable that obeys strict parameter definitions and MUST accept event parameters exactly as documented. The event callback functions MUST NOT throw an Exception. The return value of the event callback functions will be ignored and has no effect, so for performance reasons you're recommended to not return any excessive data structures.

Every implementation of this interface MUST follow these event semantics in order to be considered a well-behaving stream.

Note that higher-level implementations of this interface may choose to define additional events with dedicated semantics not defined as part of this low-level stream specification. Conformance with these event semantics is out of scope for this interface, so you may also have to refer to the documentation of such a higher-level implementation.

The drain event will be emitted whenever the write buffer became full previously and is now ready to accept more data.

$stream->on('drain', function () use ($stream): void {
    echo 'Stream is now ready to accept more data';
});

This event SHOULD be emitted once every time the buffer became full previously and is now ready to accept more data. In other words, this event MAY be emitted any number of times, which may be zero times if the buffer never became full in the first place. This event SHOULD NOT be emitted if the buffer has not become full previously.

This event is mostly used internally, see also write() for more details.

The pipe event will be emitted whenever a readable stream is pipe()d into this stream. The event receives a single ReadableStreamInterface argument for the source stream.

$stream->on('pipe', function (ReadableStreamInterface $source) use ($stream): void {
    echo 'Now receiving piped data';

    // explicitly close target if source emits an error
    $source->on('error', function () use ($stream): void {
        $stream->close();
    });
});

$source->pipe($stream);

This event MUST be emitted once for each readable stream that is successfully piped into this destination stream. In other words, this event MAY be emitted any number of times, which may be zero times if no stream is ever piped into this stream. This event MUST NOT be emitted if either the source is not readable (closed already) or this destination is not writable (closed already).

This event is mostly used internally, see also pipe() for more details.

The error event will be emitted once a fatal error occurs, usually while trying to write to this stream. The event receives a single Exception argument for the error instance.

$stream->on('error', function (Exception $e): void {
    echo 'Error: ' . $e->getMessage() . PHP_EOL;
});

This event SHOULD be emitted once the stream detects a fatal error, such as a fatal transmission error. It SHOULD NOT be emitted after a previous error or close event. It MUST NOT be emitted if this is not a fatal error condition, such as a temporary network issue that did not cause any data to be lost.

After the stream errors, it MUST close the stream and SHOULD thus be followed by a close event and then switch to non-writable mode, see also close() and isWritable().

Many common streams (such as a TCP/IP connection or a file-based stream) only deal with data transmission and may choose to only emit this for a fatal transmission error once and will then close (terminate) the stream in response.

If this stream is a DuplexStreamInterface, you should also notice how the readable side of the stream also implements an error event. In other words, an error may occur while either reading or writing the stream which should result in the same error processing.

The close event will be emitted once the stream closes (terminates).

$stream->on('close', function (): void {
    echo 'CLOSED';
});

This event SHOULD be emitted once or never at all, depending on whether the stream ever terminates. It SHOULD NOT be emitted after a previous close event.

After the stream is closed, it MUST switch to non-writable mode, see also isWritable().

This event SHOULD be emitted whenever the stream closes, irrespective of whether this happens implicitly due to an unrecoverable error or explicitly when either side closes the stream.

Many common streams (such as a TCP/IP connection or a file-based stream) will likely choose to emit this event after flushing the buffer from the end() method, after receiving a successful end event or after a fatal transmission error event.

If this stream is a DuplexStreamInterface, you should also notice how the readable side of the stream also implements a close event. In other words, after receiving this event, the stream MUST switch into non-writable AND non-readable mode, see also isReadable(). Note that this event should not be confused with the end event.

The isWritable(): bool method can be used to check whether this stream is in a writable state (not closed already).

This method can be used to check if the stream still accepts writing any data or if it is ended or closed already. Writing any data to a non-writable stream is a NO-OP:

assert($stream->isWritable() === false);

$stream->write('end'); // NO-OP
$stream->end('end'); // NO-OP

A successfully opened stream always MUST start in writable mode.

Once the stream ends or closes, it MUST switch to non-writable mode. This can happen any time, explicitly through end() or close() or implicitly due to a remote close or an unrecoverable transmission error. Once a stream has switched to non-writable mode, it MUST NOT transition back to writable mode.

If this stream is a DuplexStreamInterface, you should also notice how the readable side of the stream also implements an isReadable() method. Unless this is a half-open duplex stream, they SHOULD usually have the same return value.

The write(mixed $data): bool method can be used to write some data into the stream.

A successful write MUST be confirmed with a boolean true, which means that either the data was written (flushed) immediately or is buffered and scheduled for a future write. Note that this interface gives you no control over explicitly flushing the buffered data, as finding the appropriate time for this is beyond the scope of this interface and left up to the implementation of this interface.

Many common streams (such as a TCP/IP connection or file-based stream) may choose to buffer all given data and schedule a future flush by using an underlying EventLoop to check when the resource is actually writable.

If a stream cannot handle writing (or flushing) the data, it SHOULD emit an error event and MAY close() the stream if it can not recover from this error.

If the internal buffer is full after adding $data, then write() SHOULD return false, indicating that the caller should stop sending data until the buffer drains. The stream SHOULD send a drain event once the buffer is ready to accept more data.

Similarly, if the stream is not writable (already in a closed state) it MUST NOT process the given $data and SHOULD return false, indicating that the caller should stop sending data.

The given $data argument MAY be of mixed type, but it's usually recommended it SHOULD be a string value or MAY use a type that allows representation as a string for maximum compatibility.

Many common streams (such as a TCP/IP connection or a file-based stream) will only accept the raw (binary) payload data that is transferred over the wire as chunks of string values.

Due to the stream-based nature of this, the sender may send any number of chunks with varying sizes. There are no guarantees that these chunks will be received with the exact same framing the sender intended to send. In other words, many lower-level protocols (such as TCP/IP) transfer the data in chunks that may be anywhere between single-byte values to several dozens of kilobytes. You may want to apply a higher-level protocol to these low-level data chunks in order to achieve proper message framing.

The end(mixed $data = null): void method can be used to successfully end the stream (after optionally sending some final data).

This method can be used to successfully end the stream, i.e. close the stream after sending out all data that is currently buffered.

$stream->write('hello');
$stream->write('world');
$stream->end();

If there's no data currently buffered and nothing to be flushed, then this method MAY close() the stream immediately.

If there's still data in the buffer that needs to be flushed first, then this method SHOULD try to write out this data and only then close() the stream. Once the stream is closed, it SHOULD emit a close event.

Note that this interface gives you no control over explicitly flushing the buffered data, as finding the appropriate time for this is beyond the scope of this interface and left up to the implementation of this interface.

Many common streams (such as a TCP/IP connection or file-based stream) may choose to buffer all given data and schedule a future flush by using an underlying EventLoop to check when the resource is actually writable.

You can optionally pass some final data that is written to the stream before ending the stream. If a non-null value is given as $data, then this method will behave just like calling write($data) before ending with no data.

// shorter version
$stream->end('bye');

// same as longer version
$stream->write('bye');
$stream->end();

After calling this method, the stream MUST switch into a non-writable mode, see also isWritable(). This means that no further writes are possible, so any additional write() or end() calls have no effect.

$stream->end();
assert($stream->isWritable() === false);

$stream->write('nope'); // NO-OP
$stream->end(); // NO-OP

If this stream is a DuplexStreamInterface, calling this method SHOULD also end its readable side, unless the stream supports half-open mode. In other words, after calling this method, these streams SHOULD switch into non-writable AND non-readable mode, see also isReadable(). This implies that in this case, the stream SHOULD NOT emit any data or end events anymore. Streams MAY choose to use the pause() method logic for this, but special care may have to be taken to ensure a following call to the resume() method SHOULD NOT continue emitting readable events.

Note that this method should not be confused with the close() method.

The close(): void method can be used to close the stream (forcefully).

This method can be used to forcefully close the stream, i.e. close the stream without waiting for any buffered data to be flushed. If there's still data in the buffer, this data SHOULD be discarded.

$stream->close();

Once the stream is closed, it SHOULD emit a close event. Note that this event SHOULD NOT be emitted more than once, in particular if this method is called multiple times.

After calling this method, the stream MUST switch into a non-writable mode, see also isWritable(). This means that no further writes are possible, so any additional write() or end() calls have no effect.

$stream->close();
assert($stream->isWritable() === false);

$stream->write('nope'); // NO-OP
$stream->end(); // NO-OP

Note that this method should not be confused with the end() method. Unlike the end() method, this method does not take care of any existing buffers and simply discards any buffer contents. Likewise, this method may also be called after calling end() on a stream in order to stop waiting for the stream to flush its final data.

$stream->end();
Loop::addTimer(1.0, function () use ($stream): void {
    $stream->close();
});

If this stream is a DuplexStreamInterface, you should also notice how the readable side of the stream also implements a close() method. In other words, after calling this method, the stream MUST switch into non-writable AND non-readable mode, see also isReadable().

The DuplexStreamInterface is responsible for providing an interface for duplex streams (both readable and writable).

It builds on top of the existing interfaces for readable and writable streams and follows the exact same method and event semantics. If you're new to this concept, you should look into the ReadableStreamInterface and WritableStreamInterface first.

Besides defining a few methods, this interface also implements the EventEmitterInterface which allows you to react to the same events defined on the ReadbleStreamInterface and WritableStreamInterface.

The event callback functions MUST be a valid callable that obeys strict parameter definitions and MUST accept event parameters exactly as documented. The event callback functions MUST NOT throw an Exception. The return value of the event callback functions will be ignored and has no effect, so for performance reasons you're recommended to not return any excessive data structures.

Every implementation of this interface MUST follow these event semantics in order to be considered a well-behaving stream.

Note that higher-level implementations of this interface may choose to define additional events with dedicated semantics not defined as part of this low-level stream specification. Conformance with these event semantics is out of scope for this interface, so you may also have to refer to the documentation of such a higher-level implementation.

See also ReadableStreamInterface and WritableStreamInterface for more details.

ReactPHP uses the concept of "streams" throughout its ecosystem, so that many higher-level consumers of this package only deal with stream usage. This implies that stream instances are most often created within some higher-level components and many consumers never actually have to deal with creating a stream instance.

• Use react/socket if you want to accept incoming or establish outgoing plaintext TCP/IP or secure TLS socket connection streams.
• Use react/http if you want to receive an incoming HTTP request body streams.
• Use react/child-process if you want to communicate with child processes via process pipes such as STDIN, STDOUT, STDERR etc.
• Use experimental react/filesystem if you want to read from / write to the filesystem.
• See also the last chapter for more real-world applications.

However, if you are writing a lower-level component or want to create a stream instance from a stream resource, then the following chapter is for you.

Note that the following examples use fopen() and stream_socket_client() for illustration purposes only. These functions SHOULD NOT be used in a truly async program because each call may take several seconds to complete and would block the EventLoop otherwise. Additionally, the fopen() call will return a file handle on some platforms which may or may not be supported by all EventLoop implementations. As an alternative, you may want to use higher-level libraries listed above.

The ReadableResourceStream is a concrete implementation of the ReadableStreamInterface for PHP's stream resources.

This can be used to represent a read-only resource like a file stream opened in readable mode or a stream such as STDIN:

$stream = new ReadableResourceStream(STDIN);
$stream->on('data', function (string $chunk): void {
    echo $chunk;
});
$stream->on('end', function (): void {
    echo 'END';
});

See also ReadableStreamInterface for more details.

The first parameter given to the constructor MUST be a valid stream resource that is opened in reading mode (e.g. fopen() mode r). Otherwise, it will throw an InvalidArgumentException:

// throws InvalidArgumentException
$stream = new ReadableResourceStream(false);

See also the DuplexResourceStream for read-and-write stream resources otherwise.

Internally, this class tries to enable non-blocking mode on the stream resource which may not be supported for all stream resources. Most notably, this is not supported by pipes on Windows (STDIN etc.). If this fails, it will throw a