diff --git a/.travis.yml b/.travis.yml
index b51dcb9b..7af713a4 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,6 +1,7 @@
 language: php
 
 php:
+# - 5.3 # requires old distro, see below
   - 5.4
   - 5.5
   - 5.6
@@ -13,6 +14,9 @@ php:
 dist: trusty
 
 matrix:
+  include:
+    - php: 5.3
+      dist: precise
   allow_failures:
     - php: hhvm
 
diff --git a/README.md b/README.md
index 7d7e0f38..7a30ec15 100644
--- a/README.md
+++ b/README.md
@@ -158,7 +158,7 @@ A `stream_select()` based event loop.
 This uses the [`stream_select()`](http://php.net/manual/en/function.stream-select.php)
 function and is the only implementation which works out of the box with PHP.
 
-This event loop works out of the box on PHP 5.4 through PHP 7+ and HHVM.
+This event loop works out of the box on PHP 5.3 through PHP 7+ and HHVM.
 This means that no installation is required and this library works on all
 platforms and supported PHP versions.
 Accordingly, the [`Factory`](#factory) will use this event loop by default if
@@ -574,7 +574,7 @@ $ composer require react/event-loop
 ```
 
 This project aims to run on any platform and thus does not require any PHP
-extensions and supports running on legacy PHP 5.4 through current PHP 7+ and
+extensions and supports running on legacy PHP 5.3 through current PHP 7+ and
 HHVM.
 It's *highly recommended to use PHP 7+* for this project.
 
diff --git a/composer.json b/composer.json
index ad14cf4b..05afe65a 100644
--- a/composer.json
+++ b/composer.json
@@ -4,7 +4,7 @@
     "keywords": ["event-loop", "asynchronous"],
     "license": "MIT",
     "require": {
-        "php": ">=5.4.0"
+        "php": ">=5.3.0"
     },
     "require-dev": {
         "phpunit/phpunit": "~4.8.35 || ^5.7 || ^6.4"
diff --git a/src/ExtEventLoop.php b/src/ExtEventLoop.php
index 53bbc974..4146fc18 100644
--- a/src/ExtEventLoop.php
+++ b/src/ExtEventLoop.php
@@ -26,15 +26,15 @@ final class ExtEventLoop implements LoopInterface
     private $timerCallback;
     private $timerEvents;
     private $streamCallback;
-    private $readEvents = [];
-    private $writeEvents = [];
-    private $readListeners = [];
-    private $writeListeners = [];
-    private $readRefs = [];
-    private $writeRefs = [];
+    private $readEvents = array();
+    private $writeEvents = array();
+    private $readListeners = array();
+    private $writeListeners = array();
+    private $readRefs = array();
+    private $writeRefs = array();
     private $running;
     private $signals;
-    private $signalEvents = [];
+    private $signalEvents = array();
 
     public function __construct(EventBaseConfig $config = null)
     {
@@ -215,10 +215,11 @@ private function scheduleTimer(TimerInterface $timer)
      */
     private function createTimerCallback()
     {
-        $this->timerCallback = function ($_, $__, $timer) {
+        $timers = $this->timerEvents;
+        $this->timerCallback = function ($_, $__, $timer) use ($timers) {
             call_user_func($timer->getCallback(), $timer);
 
-            if (!$timer->isPeriodic() && $this->timerEvents->contains($timer)) {
+            if (!$timer->isPeriodic() && $timers->contains($timer)) {
                 $this->cancelTimer($timer);
             }
         };
@@ -233,15 +234,17 @@ private function createTimerCallback()
      */
     private function createStreamCallback()
     {
-        $this->streamCallback = function ($stream, $flags) {
+        $read =& $this->readListeners;
+        $write =& $this->writeListeners;
+        $this->streamCallback = function ($stream, $flags) use (&$read, &$write) {
             $key = (int) $stream;
 
-            if (Event::READ === (Event::READ & $flags) && isset($this->readListeners[$key])) {
-                call_user_func($this->readListeners[$key], $stream);
+            if (Event::READ === (Event::READ & $flags) && isset($read[$key])) {
+                call_user_func($read[$key], $stream);
             }
 
-            if (Event::WRITE === (Event::WRITE & $flags) && isset($this->writeListeners[$key])) {
-                call_user_func($this->writeListeners[$key], $stream);
+            if (Event::WRITE === (Event::WRITE & $flags) && isset($write[$key])) {
+                call_user_func($write[$key], $stream);
             }
         };
     }
diff --git a/src/ExtLibevLoop.php b/src/ExtLibevLoop.php
index 587bb044..9c679895 100644
--- a/src/ExtLibevLoop.php
+++ b/src/ExtLibevLoop.php
@@ -28,11 +28,11 @@ final class ExtLibevLoop implements LoopInterface
     private $loop;
     private $futureTickQueue;
     private $timerEvents;
-    private $readEvents = [];
-    private $writeEvents = [];
+    private $readEvents = array();
+    private $writeEvents = array();
     private $running;
     private $signals;
-    private $signalEvents = [];
+    private $signalEvents = array();
 
     public function __construct()
     {
@@ -100,11 +100,13 @@ public function addTimer($interval, $callback)
     {
         $timer = new Timer( $interval, $callback, false);
 
-        $callback = function () use ($timer) {
+        $that = $this;
+        $timers = $this->timerEvents;
+        $callback = function () use ($timer, $timers, $that) {
             call_user_func($timer->getCallback(), $timer);
 
-            if ($this->timerEvents->contains($timer)) {
-                $this->cancelTimer($timer);
+            if ($timers->contains($timer)) {
+                $that->cancelTimer($timer);
             }
         };
 
@@ -148,8 +150,9 @@ public function addSignal($signal, $listener)
         $this->signals->add($signal, $listener);
 
         if (!isset($this->signalEvents[$signal])) {
-            $this->signalEvents[$signal] = new SignalEvent(function () use ($signal) {
-                $this->signals->call($signal);
+            $signals = $this->signals;
+            $this->signalEvents[$signal] = new SignalEvent(function () use ($signals, $signal) {
+                $signals->call($signal);
             }, $signal);
             $this->loop->add($this->signalEvents[$signal]);
         }
diff --git a/src/ExtLibeventLoop.php b/src/ExtLibeventLoop.php
index da181a28..5bc265e2 100644
--- a/src/ExtLibeventLoop.php
+++ b/src/ExtLibeventLoop.php
@@ -42,13 +42,13 @@ final class ExtLibeventLoop implements LoopInterface
     private $timerCallback;
     private $timerEvents;
     private $streamCallback;
-    private $readEvents = [];
-    private $writeEvents = [];
-    private $readListeners = [];
-    private $writeListeners = [];
+    private $readEvents = array();
+    private $writeEvents = array();
+    private $readListeners = array();
+    private $writeListeners = array();
     private $running;
     private $signals;
-    private $signalEvents = [];
+    private $signalEvents = array();
 
     public function __construct()
     {
@@ -228,24 +228,26 @@ private function scheduleTimer(TimerInterface $timer)
      */
     private function createTimerCallback()
     {
-        $this->timerCallback = function ($_, $__, $timer) {
+        $that = $this;
+        $timers = $this->timerEvents;
+        $this->timerCallback = function ($_, $__, $timer) use ($timers, $that) {
             call_user_func($timer->getCallback(), $timer);
 
             // Timer already cancelled ...
-            if (!$this->timerEvents->contains($timer)) {
+            if (!$timers->contains($timer)) {
                 return;
             }
 
             // Reschedule periodic timers ...
             if ($timer->isPeriodic()) {
                 event_add(
-                    $this->timerEvents[$timer],
-                    $timer->getInterval() * self::MICROSECONDS_PER_SECOND
+                    $timers[$timer],
+                    $timer->getInterval() * ExtLibeventLoop::MICROSECONDS_PER_SECOND
                 );
 
             // Clean-up one shot timers ...
             } else {
-                $this->cancelTimer($timer);
+                $that->cancelTimer($timer);
             }
         };
     }
@@ -259,15 +261,17 @@ private function createTimerCallback()
      */
     private function createStreamCallback()
     {
-        $this->streamCallback = function ($stream, $flags) {
+        $read =& $this->readListeners;
+        $write =& $this->writeListeners;
+        $this->streamCallback = function ($stream, $flags) use (&$read, &$write) {
             $key = (int) $stream;
 
-            if (EV_READ === (EV_READ & $flags) && isset($this->readListeners[$key])) {
-                call_user_func($this->readListeners[$key], $stream);
+            if (EV_READ === (EV_READ & $flags) && isset($read[$key])) {
+                call_user_func($read[$key], $stream);
             }
 
-            if (EV_WRITE === (EV_WRITE & $flags) && isset($this->writeListeners[$key])) {
-                call_user_func($this->writeListeners[$key], $stream);
+            if (EV_WRITE === (EV_WRITE & $flags) && isset($write[$key])) {
+                call_user_func($write[$key], $stream);
             }
         };
     }
diff --git a/src/SignalsHandler.php b/src/SignalsHandler.php
index 2614e03c..523e1ca1 100644
--- a/src/SignalsHandler.php
+++ b/src/SignalsHandler.php
@@ -7,12 +7,12 @@
  */
 final class SignalsHandler
 {
-    private $signals = [];
+    private $signals = array();
 
     public function add($signal, $listener)
     {
         if (!isset($this->signals[$signal])) {
-            $this->signals[$signal] = [];
+            $this->signals[$signal] = array();
         }
 
         if (in_array($listener, $this->signals[$signal])) {
diff --git a/src/StreamSelectLoop.php b/src/StreamSelectLoop.php
index 55bb1b8a..e82e9e47 100644
--- a/src/StreamSelectLoop.php
+++ b/src/StreamSelectLoop.php
@@ -56,10 +56,10 @@ final class StreamSelectLoop implements LoopInterface
 
     private $futureTickQueue;
     private $timers;
-    private $readStreams = [];
-    private $readListeners = [];
-    private $writeStreams = [];
-    private $writeListeners = [];
+    private $readStreams = array();
+    private $readListeners = array();
+    private $writeStreams = array();
+    private $writeListeners = array();
     private $running;
     private $pcntl = false;
     private $signals;
diff --git a/tests/AbstractLoopTest.php b/tests/AbstractLoopTest.php
index 6cac6eb1..2a30b48c 100644
--- a/tests/AbstractLoopTest.php
+++ b/tests/AbstractLoopTest.php
@@ -82,14 +82,16 @@ private function subAddReadStreamReceivesDataFromStreamReference()
         fwrite($input, 'hello');
         fclose($input);
 
-        $this->loop->addReadStream($output, function ($output) {
+        $loop = $this->loop;
+        $received =& $this->received;
+        $loop->addReadStream($output, function ($output) use ($loop, &$received) {
             $chunk = fread($output, 1024);
             if ($chunk === '') {
-                $this->received .= 'X';
-                $this->loop->removeReadStream($output);
+                $received .= 'X';
+                $loop->removeReadStream($output);
                 fclose($output);
             } else {
-                $this->received .= '[' . $chunk . ']';
+                $received .= '[' . $chunk . ']';
             }
         });
     }
@@ -194,9 +196,10 @@ public function testRemoveReadAndWriteStreamFromLoopOnceResourceClosesEndsLoop()
         $this->loop->addWriteStream($stream, function () { });
 
         // remove stream when the stream is readable (closes)
-        $this->loop->addReadStream($stream, function ($stream) {
-            $this->loop->removeReadStream($stream);
-            $this->loop->removeWriteStream($stream);
+        $loop = $this->loop;
+        $loop->addReadStream($stream, function ($stream) use ($loop) {
+            $loop->removeReadStream($stream);
+            $loop->removeWriteStream($stream);
             fclose($stream);
         });
 
@@ -216,14 +219,15 @@ public function testRemoveReadAndWriteStreamFromLoopOnceResourceClosesOnEndOfFil
         $this->loop->addWriteStream($stream, function () { });
 
         // remove stream when the stream is readable (closes)
-        $this->loop->addReadStream($stream, function ($stream) {
+        $loop = $this->loop;
+        $loop->addReadStream($stream, function ($stream) use ($loop) {
             $data = fread($stream, 1024);
             if ($data !== '') {
                 return;
             }
 
-            $this->loop->removeReadStream($stream);
-            $this->loop->removeWriteStream($stream);
+            $loop->removeReadStream($stream);
+            $loop->removeWriteStream($stream);
             fclose($stream);
         });
 
@@ -246,9 +250,10 @@ public function testRemoveReadAndWriteStreamFromLoopWithClosingResourceEndsLoop(
         $this->loop->addWriteStream($stream, function () { });
 
         // remove stream when the stream is readable (closes)
-        $this->loop->addReadStream($stream, function ($stream) {
-            $this->loop->removeReadStream($stream);
-            $this->loop->removeWriteStream($stream);
+        $loop = $this->loop;
+        $loop->addReadStream($stream, function ($stream) use ($loop) {
+            $loop->removeReadStream($stream);
+            $loop->removeWriteStream($stream);
             fclose($stream);
         });
 
@@ -304,16 +309,18 @@ public function stopShouldStopRunningLoop()
 
     public function testStopShouldPreventRunFromBlocking()
     {
+        $that = $this;
         $this->loop->addTimer(
             1,
-            function () {
-                $this->fail('Timer was executed.');
+            function () use ($that) {
+                $that->fail('Timer was executed.');
             }
         );
 
+        $loop = $this->loop;
         $this->loop->futureTick(
-            function () {
-                $this->loop->stop();
+            function () use ($loop) {
+                $loop->stop();
             }
         );
 
@@ -338,9 +345,10 @@ public function testIgnoreRemovedCallback()
         });
 
         // this callback would have to be called as well, but the first stream already removed us
-        $loop->addReadStream($input2, function () use (& $called) {
+        $that = $this;
+        $loop->addReadStream($input2, function () use (& $called, $that) {
             if ($called) {
-                $this->fail('Callback 2 must not be called after callback 1 was called');
+                $that->fail('Callback 2 must not be called after callback 1 was called');
             }
         });
 
@@ -354,9 +362,10 @@ public function testIgnoreRemovedCallback()
 
     public function testFutureTickEventGeneratedByFutureTick()
     {
+        $loop = $this->loop;
         $this->loop->futureTick(
-            function () {
-                $this->loop->futureTick(
+            function () use ($loop) {
+                $loop->futureTick(
                     function () {
                         echo 'future-tick' . PHP_EOL;
                     }
@@ -412,18 +421,19 @@ public function testRecursiveFutureTick()
     {
         list ($stream) = $this->createSocketPair();
 
+        $loop = $this->loop;
         $this->loop->addWriteStream(
             $stream,
-            function () use ($stream) {
+            function () use ($stream, $loop) {
                 echo 'stream' . PHP_EOL;
-                $this->loop->removeWriteStream($stream);
+                $loop->removeWriteStream($stream);
             }
         );
 
         $this->loop->futureTick(
-            function () {
+            function () use ($loop) {
                 echo 'future-tick-1' . PHP_EOL;
-                $this->loop->futureTick(
+                $loop->futureTick(
                     function () {
                         echo 'future-tick-2' . PHP_EOL;
                     }
@@ -440,11 +450,12 @@ public function testRunWaitsForFutureTickEvents()
     {
         list ($stream) = $this->createSocketPair();
 
+        $loop = $this->loop;
         $this->loop->addWriteStream(
             $stream,
-            function () use ($stream) {
-                $this->loop->removeWriteStream($stream);
-                $this->loop->futureTick(
+            function () use ($stream, $loop) {
+                $loop->removeWriteStream($stream);
+                $loop->futureTick(
                     function () {
                         echo 'future-tick' . PHP_EOL;
                     }
@@ -459,10 +470,11 @@ function () {
 
     public function testFutureTickEventGeneratedByTimer()
     {
+        $loop = $this->loop;
         $this->loop->addTimer(
             0.001,
-            function () {
-                $this->loop->futureTick(
+            function () use ($loop) {
+                $loop->futureTick(
                     function () {
                         echo 'future-tick' . PHP_EOL;
                     }
@@ -496,11 +508,12 @@ public function testSignal()
             $calledShouldNot = false;
         });
 
-        $this->loop->addSignal(SIGUSR1, $func1 = function () use (&$func1, &$func2, &$called, $timer) {
+        $loop = $this->loop;
+        $this->loop->addSignal(SIGUSR1, $func1 = function () use (&$func1, &$func2, &$called, $timer, $loop) {
             $called = true;
-            $this->loop->removeSignal(SIGUSR1, $func1);
-            $this->loop->removeSignal(SIGUSR2, $func2);
-            $this->loop->cancelTimer($timer);
+            $loop->removeSignal(SIGUSR1, $func1);
+            $loop->removeSignal(SIGUSR2, $func2);
+            $loop->cancelTimer($timer);
         });
 
         $this->loop->futureTick(function () {
@@ -527,8 +540,9 @@ public function testSignalMultipleUsagesForTheSameListener()
         $this->loop->addTimer(0.4, function () {
             posix_kill(posix_getpid(), SIGUSR1);
         });
-        $this->loop->addTimer(0.9, function () use (&$func) {
-            $this->loop->removeSignal(SIGUSR1, $func);
+        $loop = $this->loop;
+        $this->loop->addTimer(0.9, function () use (&$func, $loop) {
+            $loop->removeSignal(SIGUSR1, $func);
         });
 
         $this->loop->run();
@@ -538,11 +552,12 @@ public function testSignalMultipleUsagesForTheSameListener()
 
     public function testSignalsKeepTheLoopRunning()
     {
+        $loop = $this->loop;
         $function = function () {};
         $this->loop->addSignal(SIGUSR1, $function);
-        $this->loop->addTimer(1.5, function () use ($function) {
-            $this->loop->removeSignal(SIGUSR1, $function);
-            $this->loop->stop();
+        $this->loop->addTimer(1.5, function () use ($function, $loop) {
+            $loop->removeSignal(SIGUSR1, $function);
+            $loop->stop();
         });
 
         $this->assertRunSlowerThan(1.5);
@@ -550,10 +565,11 @@ public function testSignalsKeepTheLoopRunning()
 
     public function testSignalsKeepTheLoopRunningAndRemovingItStopsTheLoop()
     {
+        $loop = $this->loop;
         $function = function () {};
         $this->loop->addSignal(SIGUSR1, $function);
-        $this->loop->addTimer(1.5, function () use ($function) {
-            $this->loop->removeSignal(SIGUSR1, $function);
+        $this->loop->addTimer(1.5, function () use ($function, $loop) {
+            $loop->removeSignal(SIGUSR1, $function);
         });
 
         $this->assertRunFasterThan(1.6);
@@ -568,9 +584,10 @@ public function testTimerIntervalCanBeFarInFuture()
         $timer = $this->loop->addTimer(PHP_INT_MAX, function () { });
 
         // remove stream and timer when the stream is readable (closes)
-        $this->loop->addReadStream($stream, function ($stream) use ($timer) {
-            $this->loop->removeReadStream($stream);
-            $this->loop->cancelTimer($timer);
+        $loop = $this->loop;
+        $this->loop->addReadStream($stream, function ($stream) use ($timer, $loop) {
+            $loop->removeReadStream($stream);
+            $loop->cancelTimer($timer);
         });
 
         $this->assertRunFasterThan($this->tickTimeout);
diff --git a/tests/StreamSelectLoopTest.php b/tests/StreamSelectLoopTest.php
index 87bbbe69..bd19e1cd 100644
--- a/tests/StreamSelectLoopTest.php
+++ b/tests/StreamSelectLoopTest.php
@@ -39,11 +39,11 @@ public function testStreamSelectTimeoutEmulation()
 
     public function signalProvider()
     {
-        return [
-            ['SIGUSR1'],
-            ['SIGHUP'],
-            ['SIGTERM'],
-        ];
+        return array(
+            array('SIGUSR1'),
+            array('SIGHUP'),
+            array('SIGTERM'),
+        );
     }
 
     /**
@@ -60,8 +60,9 @@ public function testSignalInterruptNoStream($signal)
         $check = $this->loop->addPeriodicTimer(0.01, function() {
             pcntl_signal_dispatch();
         });
-        $this->loop->addTimer(0.1, function () use ($check) {
-            $this->loop->cancelTimer($check);
+        $loop = $this->loop;
+        $loop->addTimer(0.1, function () use ($check, $loop) {
+            $loop->cancelTimer($check);
         });
 
         $handled = false;
@@ -92,12 +93,13 @@ public function testSignalInterruptWithStream($signal)
         });
 
         // add stream to the loop
+        $loop = $this->loop;
         list($writeStream, $readStream) = $this->createSocketPair();
-        $this->loop->addReadStream($readStream, function ($stream) {
+        $loop->addReadStream($readStream, function ($stream) use ($loop) {
             /** @var $loop LoopInterface */
             $read = fgets($stream);
             if ($read === "end loop\n") {
-                $this->loop->stop();
+                $loop->stop();
             }
         });
         $this->loop->addTimer(0.1, function() use ($writeStream) {
diff --git a/travis-init.sh b/travis-init.sh
index c8c8b55d..06f853fe 100755
--- a/travis-init.sh
+++ b/travis-init.sh
@@ -6,7 +6,9 @@ if [[ "$TRAVIS_PHP_VERSION" != "hhvm" &&
       "$TRAVIS_PHP_VERSION" != "hhvm-nightly" ]]; then
 
     # install 'event' PHP extension
-    echo "yes" | pecl install event
+    if [[ "$TRAVIS_PHP_VERSION" != "5.3" ]]; then
+        echo "yes" | pecl install event
+    fi
 
     # install 'libevent' PHP extension (does not support php 7)
     if [[ "$TRAVIS_PHP_VERSION" != "7.0" &&