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PHP libev Extension

PHP extension providing an object-oriented binding to the libev event-loop library.

Still under development, may contain bugs or missing methods.

Author: Martin Wernståhl <>


./configure --with-libev
make install


All of these examples should be working.

Most of these should you be able to combine into the same loop, for example the timer and the uppercase echo. As the event loop is only firing the echo part when there is data to read the timer part will not be interrupted by the IOEvent unless its callback takes a very long time to complete (which the example here does not).

Two TimerEvents printing a message, one with 1 second interval, the other only a single message after 5 seconds.:

$loop = new libev\EventLoop();

$repeater = new libev\TimerEvent(function()
    echo "I repeat every second!\n";
}, 1, 1);

$single = new libev\TimerEvent(function()
   echo "I will fire after 5 seconds, without repeat\n";
}, 5);



Read from STDIN and print the uppercased input:

$loop = new libev\EventLoop();

$in = fopen('php://stdin', 'r');
$echo = new libev\IOEvent(function($event) use($in)
    // Read all (at most 200) and uppercase
    echo "ECHO: ".strtoupper(fread($in, 200));

}, $in, libev\IOEvent::READ);


More precise timer event:

$loop = new libev\EventLoop();

// This will trigger very close to exactly 10 seconds after
// this object has been created
$time = new libev\PeriodicEvent(function()
    echo "I was triggered!";
}, time() + 10);


Periodically switching on and off events:

$loop = new libev\EventLoop();

$period1 = new libev\TimerEvent(function()
      echo "Fast\n";
}, .1, .5);

$period2 = new libev\TimerEvent(function() use($period1, $loop)
        echo "Fast off\n";
        echo "Fast on\n";
}, 3, 3);



Combining libev\SignalEvent and libev\StatEvent to look for file changes while still performing graceful shutdown on ^C:

$loop = new libev\EventLoop();

// Watch ./test for changes
$stat = new libev\StatEvent(function() use(&$stat)
    printf("%s changed\n", './test');
}, './test');


// Graceful shutdown on ^C
$loop->add(new libev\SignalEvent(function() use($loop)
    echo "exiting\n";
}, libev\SignalEvent::SIGINT));





Creates a new EventLoop object with a new ev_loop as base.

static EventLoop EventLoop::getDefaultLoop()

Returns the default event loop object, this object is a global singleton and it is not recommended to use it unless you only use one major loop in your application or if you require ChildEvent watchers as they can only be attached to the default loop.

boolean EventLoop::notifyFork()

Notifies libev that a fork might have been done and forces it to reinitialize kernel state where needed on the next loop iteration.

boolean EventLoop::isDefaultLoop()

Returns true if the EventLoop is the default libev loop.

int EventLoop::getIteration()

Returns the current loop iteration.

int EventLoop::getDepth()

Returns the current nesting depth of event-loops.

int EventLoop::getBackend()

Returns one of the EventLoop::BACKEND_* constants indicating the event backend in use.

double EventLoop::now()

Returns the time the current loop iteration received events. Seconds in libev time.

bool EventLoop::updateNow()

Establishes the current time by querying the kernel, updating the time returned by EventLoop::now() in the progress. This is a costly operation and is usually done automatically within EventLoop::run().

This function is rarely useful, but when some event callback runs for a very long time without entering the event loop, updating libev's idea of the current time is a good idea.

bool EventLoop::suspend()

Suspends the event loop, pausing all timers and delays processing of events.


bool EventLoop::resume()

Resumes the event loop and all timers.

NOTE: DO NOT CALL UNLESS YOU HAVE CALLED EventLoop->suspend() first!

boolean EventLoop::run(flag = 0)

Runs the event loop, processing all events, will block until EventLoop->break() is called or no more events are associated with this loop by default.

libev flag:

  • int(0), default

    run() handles events until there are no events to handle

  • EventLoop::RUN_NOWAIT

    run() looks for new events, handles them and then return after one iteration of the loop

  • EventLoop::RUN_ONCE

    run() looks for new events (wait if necessary) and will handle those and any outstanding ones. It will block until at least one event has arrived and will return after one iteration of the loop

boolean EventLoop::breakLoop(flag = EventLoop::BREAK_ONE)

Breaks the current event loop after it has processed all outstanding events.

libev break flag:

  • EventLoop::BREAK_ONE: will break the innermost loop, default behaviour
  • EventLoop::BREAK_ALL: will break all the currently running loops

boolean EventLoop::ref() and boolean EventLoop::unref()

Ref/unref can be used to add or remove a reference count on the event loop: Every Event keeps one reference, and as long as the reference count is nonzero, EventLoop::run() will not return on its own.

This is useful when you have an Event that you never intend to remove, but that nevertheless should not keep EventLoop::run() from returning. In such a case, call EventLoop::unref() after starting, and EventLoop::ref() before stopping it.

Example: Create a signal watcher, but prevent it from keeping EventLoop::run() running when nothing else is active:

$sig = new libev\SignalEvent(libev\SignalEvent::SIGINT, function()
    // Do something


// For some weird reason we want to unregister the above handler
$sig->stop();  // or $loop->remove($sig);

boolean EventLoop::setIOCollectInterval(double = 0)

Sets the time libev spends sleeping for new IO events between loop iterations, seconds.

boolean EventLoop::setTimeoutCollectInterval(double = 0)

Sets the time libev spends sleeping for new timeout events between loop iterations, seconds.

int EventLoop::getPendingCount()

Returns the number of pending events.

boolean EventLoop::add(libevEvent)

Adds the event to the event loop.

This method will increase the refcount on the supplied Event, protecting it from garbage collection. Refcount will be decreased on EventLoop::remove() or when the EventLoop object is Garbage Collected.

It is recommended to keep a variable pointing to each recurring event you add to the loop to be able to remove them when you need to.

The callback of the events can also remove it, because it receives the Event object as its only parameter you can do:

$timer = new libev\TimerEvent(function($event))
    if( /* some condition */ )
}, 1, 1);

boolean EventLoop::remove(libevEvent)

Removes the event from the event loop, will skip all pending events on it too.

boolean EventLoop::clearPending(libevEvent)

If the watcher is pending, this function clears its pending status and returns its revents bitset (as if its callback was invoked). If the watcher isn't pending it returns 0, or if it is not associated with this EventLoop it returns false.

boolean EventLoop::feedEvent(libevEvent)

Feeds the given event set into the event loop, as if the specified event had happened for the specified watcher.

The watcher will be GC protected until it has fired or clearPending is called on it (unless you feed it again in the callback or add() it to an event loop it won't accidentally be freed).

NOTE: As of libev 4.04; If you feed an event in the callback of a fed event, the newly fed event will be invoked before any other events (except other fed events). So do NOT create loops by re-feeding an event into the EventLoop

array(libev/Event) EventLoop::getEvents()

Returns a list of all registered events.


Abstract base class for all event objects.

All Event objects have a callback associated with them which will be invoked when the Event is triggered.

Callback signature callback(libev\Event $triggered, int $revents).

TODO: More here?

boolean Event::isActive()

Returns true if the event is active, ie. associated with an event loop.

boolean Event::isPending()

Returns true if the event watcher is pending (ie. it has outstanding events but the callback has not been called yet).

int Event::clearPending()

If the Event is pending, this function clears its pending status and returns its $revents bitset (as if its callback was invoked). If the Event is not pending 0 is returned.

void Event::setCallback(callback)

Replaces the PHP callback on an event.

boolean Event::invoke()

Invokes the callback on this event, Event does not need to be attached to any EventLoop for this to work (disregarding requirments of the associated callback itself).

boolean Event::stop()

If the event has been add()``ed or ``feed_event()``ed to any ``EventLoop it will be stopped and reset.

libev\IOEvent extends libev\Event

IOEvent::__construct(callback, resource, flag)

Creates an IO event which will trigger when there is data to read and/or data to write on the supplied stream.

flag is an integer field with either IOEvent::READ and/or IOEvent::WRITE depending on the types of events you want to listen to.

resource is a valid PHP stream resource.

libev\TimerEvent extends libev\Event

TimerEvent::__construct(callback, double after, double repeat = 0)

Creates a timer event which will occur approximately after after seconds and after that will repeat with an approximate interval of repeat.

after is the time before first triggering, seconds.

interval is the time between repeats, seconds. Default is 0, which equals no repeating event.

double TimerEvent::getRepeat() and void TimerEvent::setRepeat()

Gets/sets the seconds between event triggering.

double|false TimerEvent::getAfter()

Returns the time from the loop start until the first triggering of this TimerEvent.

False is returned if the event has not been registered with any EventLoop

boolean TimerEvent::again()

This will act as if the timer timed out and restarts it again if it is repeating.

The exact semantics are:
  • If the timer is pending, its pending status is cleared.
  • If the timer is started but non-repeating, stop it (as if it timed out).
  • If the timer is repeating, either start it if necessary (with the repeat value), or reset the running timer to the repeat value.

See <> for more information.

double|false TimerEvent::getRemaining()

Returns the remaining time until the timer fire, relative to the event loop time. Returns false if the event is not registered with any EventLoop.

libev\PeriodicEvent extends libev\Event

Schedules an event (or a repeating series of events) at a specific point in time.

PeriodicEvent::__construct(callback, double offset, double interval = 0)

  • Absolute timer (offset = absolute time, interval = 0) In this configuration the watcher triggers an event after the wall clock time offset has passed. It will not repeat and will not adjust when a time jump occurs, that is, if it is to be run at January 1st 2011 then it will be stopped and invoked when the system clock reaches or surpasses this point in time.
  • Repeating interval timer (offset = offset within interval, interval > 0) In this mode the watcher will always be scheduled to time out at the next offset + N * interval time (for some integer N, which can also be negative) and then repeat, regardless of any time jumps. The offset argument is merely an offset into the interval periods.

double PeriodicEvent::getTime()

Returns the time for the next trigger of the event, seconds.

double PeriodicEvent::getOffset()

When repeating, returns the offset, otherwise it returns the absolute time for the event trigger.

double PeriodicEvent::getInterval()

When repeating, returns the current interval value.

boolean PeriodicEvent::setInterval(double)

Sets the interval value, changes only take effect when the event has fired.

boolean PeriodicEvent::again()

Works like the TimerEvent::again(), see libev\TimerEvent::again() for more information.

double|false PeriodicEvent::getRemaining()

Returns the remaining time until the timer fire, relative to the event loop time. Returns false if the event is not registered with any EventLoop.

libev\SignalEvent extends libev\Event

SignalEvent::__construct(callback, signal)

This event will be triggered when the process receives the specificed signal signal.

signal is a SignalEvent class constant, the presense or absense of some of the constants match the presense or absense of them in the system's signal.h header.

For now, you can use this code to see which constans are defined:

$class = new ReflectionClass('libev\\SignalEvent');

libev\ChildEvent extends libev\Event

This event will be triggered on child status changes.

NOTE: Must be attached to the default loop (ie. the instance from EventLoop::getDefaultLoop())

ChildEvent::__construct(callback, int pid, boolean trace = false)

pid is the PID of the child process to watch, 0 if you want the event to trigger for any child process.

If trace is true, then this event is also triggered on suspend/continue and not only terminate.

int ChildEvent::getPid()

Returns the PID of the watched child process.

int ChildEvent::getRPid()

Returns the PID of the child which caused the last event trigger.

int ChildEvent::getRStatus()

Returns the exit/trace status (see waitpid and sys/wait.h) caused by the child ChildEvent::getRPid().

libev\StatEvent extends libev\Event

Watches a file system path for attribute changes, triggers when at least one attribute has been changed.

The path does not need to exist, and the event will be triggered when the path starts to exist.

The portable implementation of ev_stat is using the system stat() call to regularily poll the path for changes which is inefficient. But even with OS supported change notifications it can be resource-intensive if many StatEvent watchers are used.

If inotify is supported and is compiled into libev that will be used instead of stat() where possible.

NOTE: When libev is doing the stat() call the loop will be blocked, so it is not recommended to use it on network resources as there might be a long delay (accoring to libev manual, it usually takes several milliseconds on a network resource, in best cases)

stat() system calls also only supports full-second resolution portably, meaning that if the time is the only thing which changes on the file several updates of it close in time might be missed because stat() still returns the same full second, unless the file changes in other ways too.

One solution to this problem is to start a timer which triggers after roughly a one-second delay (recommended to be a bit grater than 1.0 seconds because Linux gettimeofday() might return a different time from time(), the libev manual recommends 1.02)

StatEvent::__construct(callback, string file, double interval = libev_default_stat_interval)

interval is the minimum interval libev will check for file-changes, will automatically be set to the default value by libev if the supplied value is smaller than the default.

string StatEvent::getPath()

double StatEvent::getInterval()

array StatEvent::getAttr()

Returns a key => value list of the file attributes, all keys will be 0 if the event has not yet been added to an EventLoop.

The following attributes are supported:

  • dev
  • ino
  • mode
  • nlink
  • uid
  • gid
  • rdev
  • size
  • atime
  • mtime
  • ctime

NOTE: If nlink is 0, the file does not exist and the rest of the values may be inaccurate as they might remain from the file which existed during previous events.

array StatEvent::getPrev()

Returns the previous file attributes, all keys will be 0 if the event has not yet been added to an EventLoop.

libev\IdleEvent extends libev\Event

IdleEvent triggers when no other events of the same or higher priority are pending (other idle watchers do not count as receiving "events").

That is, as long as your process is busy handling sockets or timeouts (or even signals, imagine) of the same or higher priority it will not be triggered. But when your process is idle (or only lower-priority watchers are pending), the idle watchers are being called once per event loop iteration - until stopped, that is, or your process receives more events and becomes busy again with higher priority stuff.

The most noteworthy effect is that as long as any idle watchers are active, the process will not block when waiting for new events.

Apart from keeping your process non-blocking (which is a useful effect on its own sometimes), idle watchers are a good place to do "pseudo-background processing", or delay processing stuff to after the event loop has handled all outstanding events.



libev\CleanupEvent extends libev\Event

CleanupEvent is triggered just before the EventLoop object is destroyed by the PHP GC (ie. when the loop is no longer used).

There is no guarantee that the callback will be called (eg. in case of fatal PHP errors or similar things), but it provides a conventient way to associate cleanup code with the event loop.



libev\AsyncEvent extends libev\Event

AsyncEvent are Event objects which wait for a signal from another part of the application before firing. It is triggered with the AsyncEvent::send() method and will invoke the callback on the next loop iteration.

AsyncEvent instances can be activated as many times as needed, they will not be removed from the EventLoop unless manually removed.



bool AsyncEvent::send()

Tells the AsyncEvent that its callback should be invoked on the next loop iteration.


PHP extension providing an object-oriented binding to the libev event-loop library.






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