diff --git a/.travis.yml b/.travis.yml
index d2fb756..3fd6699 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,6 +1,7 @@
 language: php
 
 php:
+  - 5.3
   - 5.4
   - 5.5
   - 5.6
diff --git a/composer.json b/composer.json
index 50f166e..9a79023 100644
--- a/composer.json
+++ b/composer.json
@@ -4,10 +4,13 @@
     "keywords": ["process"],
     "license": "MIT",
     "require": {
-        "php": ">=5.4.0",
-        "evenement/evenement": "~2.0",
-        "react/event-loop": "0.4.*",
-        "react/stream": "0.4.*"
+        "php": ">=5.3.0",
+        "evenement/evenement": "~1.0",
+        "react/event-loop": "0.3.*",
+        "react/stream": "0.3.*"
+    },
+    "require-dev": {
+        "sebastian/environment": "~1.0"
     },
     "autoload": {
         "psr-4": { "React\\ChildProcess\\": "src" }
diff --git a/src/Process.php b/src/Process.php
index b6cb8d9..a4405e8 100644
--- a/src/Process.php
+++ b/src/Process.php
@@ -110,11 +110,12 @@ public function start(LoopInterface $loop, $interval = 0.1)
             stream_set_blocking($pipe, 0);
         }
 
-        $loop->addPeriodicTimer($interval, function (Timer $timer) {
-            if (!$this->isRunning()) {
-                $this->close();
+        $that = $this;
+        $loop->addPeriodicTimer($interval, function (Timer $timer) use ($that) {
+            if (!$that->isRunning()) {
+                $that->close();
                 $timer->cancel();
-                $this->emit('exit', array($this->getExitCode(), $this->getTermSignal()));
+                $that->emit('exit', array($that->getExitCode(), $that->getTermSignal()));
             }
         });
     }
diff --git a/tests/AbstractProcessTest.php b/tests/AbstractProcessTest.php
index 5948209..579e4ea 100644
--- a/tests/AbstractProcessTest.php
+++ b/tests/AbstractProcessTest.php
@@ -4,6 +4,7 @@
 
 use React\ChildProcess\Process;
 use React\EventLoop\Timer\Timer;
+use SebastianBergmann\Environment\Runtime;
 
 abstract class AbstractProcessTest extends \PHPUnit_Framework_TestCase
 {
@@ -67,7 +68,7 @@ public function testGetTermSignalWhenRunning($process)
 
     public function testProcessWithDefaultCwdAndEnv()
     {
-        $cmd = PHP_BINARY . ' -r ' . escapeshellarg('echo getcwd(), PHP_EOL, count($_SERVER), PHP_EOL;');
+        $cmd = $this->getPhpBinary() . ' -r ' . escapeshellarg('echo getcwd(), PHP_EOL, count($_SERVER), PHP_EOL;');
 
         $loop = $this->createLoop();
         $process = new Process($cmd);
@@ -95,7 +96,7 @@ public function testProcessWithDefaultCwdAndEnv()
 
     public function testProcessWithCwd()
     {
-        $cmd = PHP_BINARY . ' -r ' . escapeshellarg('echo getcwd(), PHP_EOL;');
+        $cmd = $this->getPhpBinary() . ' -r ' . escapeshellarg('echo getcwd(), PHP_EOL;');
 
         $loop = $this->createLoop();
         $process = new Process($cmd, '/');
@@ -120,7 +121,7 @@ public function testProcessWithEnv()
             $this->markTestSkipped('Cannot execute PHP processes with custom environments on Travis CI.');
         }
 
-        $cmd = PHP_BINARY . ' -r ' . escapeshellarg('echo getenv("foo"), PHP_EOL;');
+        $cmd = $this->getPhpBinary() . ' -r ' . escapeshellarg('echo getenv("foo"), PHP_EOL;');
 
         $loop = $this->createLoop();
         $process = new Process($cmd, null, array('foo' => 'bar'));
@@ -267,21 +268,22 @@ public function testTerminateWithStopAndContinueSignalsUsingEventLoop()
             $termSignal = func_get_arg(1);
         });
 
-        $loop->addTimer(0.001, function(Timer $timer) use ($process) {
+        $that = $this;
+        $loop->addTimer(0.001, function(Timer $timer) use ($process, $that) {
             $process->start($timer->getLoop());
             $process->terminate(SIGSTOP);
 
-            $this->assertSoon(function() use ($process) {
-                $this->assertTrue($process->isStopped());
-                $this->assertTrue($process->isRunning());
-                $this->assertEquals(SIGSTOP, $process->getStopSignal());
+            $that->assertSoon(function() use ($process, $that) {
+                $that->assertTrue($process->isStopped());
+                $that->assertTrue($process->isRunning());
+                $that->assertEquals(SIGSTOP, $process->getStopSignal());
             });
 
             $process->terminate(SIGCONT);
 
-            $this->assertSoon(function() use ($process) {
-                $this->assertFalse($process->isStopped());
-                $this->assertEquals(SIGSTOP, $process->getStopSignal());
+            $that->assertSoon(function() use ($process, $that) {
+                $that->assertFalse($process->isStopped());
+                $that->assertEquals(SIGSTOP, $process->getStopSignal());
             });
         });
 
@@ -325,4 +327,11 @@ public function assertSoon(\Closure $callback, $timeout = 20000, $interval = 200
             usleep($interval);
         }
     }
+
+    private function getPhpBinary()
+    {
+        $runtime = new Runtime();
+
+        return $runtime->getBinary();
+    }
 }