Add container export example

Author: clue

examples/export.php

@@ -0,0 +1,30 @@
+<?php
+// this example shows how the containerExport() call returns a TAR stream
+// and how we it can be piped into a output tar file.
+
+require __DIR__ . '/../vendor/autoload.php';
+
+use React\EventLoop\StreamSelectLoop;
+use Clue\React\Docker\Factory;
+use React\Stream\Stream;
+
+$container = isset($argv[1]) ? $argv[1] : 'asd';
+$target = isset($argv[2]) ? $argv[2] : ($container . '.tar');
+echo 'Exporting whole container "' . $container . '" to "' . $target .'" (pass as arguments to this example)' . PHP_EOL;
+
+$loop = new StreamSelectLoop();
+
+$factory = new Factory($loop);
+$client = $factory->createClient();
+
+$stream = $client->containerExportStream($container);
+
+$stream->on('error', function ($e = null) {
+    // will be called if the container is invalid/does not exist
+    echo 'ERROR requesting stream' . PHP_EOL . $e;
+});
+
+$out = new Stream(fopen($target, 'w'), $loop);
+$stream->pipe($out);
+
+$loop->run();