Throw BadMethodCallException on loop creating when required extension isn't installed

Author: WyriHaximus

README.md

@@ -149,7 +149,7 @@ You should use the [`Factory`](#factory) to automatically create a new instance.
 Advanced! If you explicitly need a certain event loop implementation, you can
 manually instantiate one of the following classes.
 Note that you may have to install the required PHP extensions for the respective
-event loop implementation first or this may result in a fatal error.
+event loop implementation first or they will throw a `BadMethodCallException` on creation.
 
 #### StreamSelectLoop
 

src/ExtEventLoop.php

@@ -2,6 +2,7 @@
 
 namespace React\EventLoop;
 
+use BadMethodCallException;
 use Event;
 use EventBase;
 use EventConfig as EventBaseConfig;
@@ -38,6 +39,10 @@ final class ExtEventLoop implements LoopInterface
 
     public function __construct()
     {
+        if (!class_exists('EventBase', false)) {
+            throw new BadMethodCallException('Cannot create ExtEventLoop, ext-event extension missing');
+        }
+
         $config = new EventBaseConfig();
         $config->requireFeatures(EventBaseConfig::FEATURE_FDS);
 

src/ExtLibevLoop.php

@@ -2,6 +2,7 @@
 
 namespace React\EventLoop;
 
+use BadMethodCallException;
 use libev\EventLoop;
 use libev\IOEvent;
 use libev\SignalEvent;
@@ -36,6 +37,10 @@ final class ExtLibevLoop implements LoopInterface
 
     public function __construct()
     {
+        if (!class_exists('libev\EventLoop', false)) {
+            throw new BadMethodCallException('Cannot create ExtLibevLoop, ext-libev extension missing');
+        }
+
         $this->loop = new EventLoop();
         $this->futureTickQueue = new FutureTickQueue();
         $this->timerEvents = new SplObjectStorage();

src/ExtLibeventLoop.php

@@ -2,6 +2,7 @@
 
 namespace React\EventLoop;
 
+use BadMethodCallException;
 use Event;
 use EventBase;
 use React\EventLoop\Tick\FutureTickQueue;
@@ -52,6 +53,10 @@ final class ExtLibeventLoop implements LoopInterface
 
     public function __construct()
     {
+        if (!function_exists('event_base_new')) {
+            throw new BadMethodCallException('Cannot create ExtLibeventLoop, ext-libevent extension missing');
+        }
+
         $this->eventBase = event_base_new();
         $this->futureTickQueue = new FutureTickQueue();
         $this->timerEvents = new SplObjectStorage();