Add Stackdriver Trace sample code for the doc (GoogleCloudPlatform#561)

* Add Stackdriver Trace sample code for the doc

* Correct the directory structure and CS fix

* Format, better comment, etc

Author: Takashi Matsuo

testing/run_test_suite.sh

@@ -65,6 +65,7 @@ do
         fi
     fi
     pushd ${DIR}
+    mkdir -p build/logs
     # Temporarily allowing error
     set +e
     if [ -f "composer.json" ]; then

trace/README.md

@@ -0,0 +1,4 @@
+# The sample code and the test for Stackdriver Trace documentation
+
+This directory holds the sample code and the test for the following page:
+https://cloud.google.com/trace/docs/setup/php

trace/composer.json

@@ -0,0 +1,6 @@
+{
+    "require": {
+        "opencensus/opencensus": "^0.2.1",
+        "google/cloud-trace": "^0.6.2"
+    }
+}

trace/phpunit.xml.dist

@@ -0,0 +1,34 @@
+xml version="1.0" encoding="UTF-8"?>
+
+<phpunit bootstrap="./vendor/autoload.php">
+    <testsuites>
+        <testsuite name="PHP Stackdriver Trace test">
+            <directory>testdirectory>
+        testsuite>
+    testsuites>
+    <logging>
+        <log type="coverage-clover" target="build/logs/clover.xml"/>
+    logging>
+    <filter>
+        <whitelist>
+            <file>trace-sample.phpfile>
+        whitelist>
+    filter>
+    <php>
+        <env name="USE_NULL_EXPORTER" value="true"/>
+    php>
+phpunit>

trace/test/TraceTest.php

@@ -0,0 +1,20 @@
+
+
+require_once __DIR__ . '/../trace-sample.php';
+
+use PHPUnit\Framework\TestCase;
+
+class TraceTest extends TestCase
+{
+    public function testTraceSample()
+    {
+        trace_callable();
+        $reflection = new \ReflectionProperty('\OpenCensus\Trace\Tracer', 'instance');
+        $reflection->setAccessible(true);
+        $handler = $reflection->getValue();
+        $tracer = $handler->tracer();
+        $spans = $tracer->spans();
+        $this->assertEquals(2, count($spans));
+        $this->assertEquals('slow_function', $spans[1]->name());
+    }
+}

trace/trace-sample.php

@@ -0,0 +1,57 @@
+
+/**
+ * Copyright 2018 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+require_once __DIR__ . '/vendor/autoload.php';
+
+use OpenCensus\Trace\Exporter\NullExporter;
+# [START trace_use_statement]
+use OpenCensus\Trace\Exporter\StackdriverExporter;
+use OpenCensus\Trace\Tracer;
+
+# [END trace_use_statement]
+
+$projectId = getenv('GOOGLE_CLOUD_PROJECT');
+if ($projectId === false) {
+    die('Set GOOGLE_CLOUD_PROJECT envvar');
+}
+
+# [START exporter_setup]
+$exporter = new StackdriverExporter([
+    'clientConfig' => [
+        'projectId' => $projectId
+    ]
+]);
+# [END exporter_setup]
+// When running tests, use a null exporter instead.
+if (getenv('USE_NULL_EXPORTER')) {
+    $exporter = new NullExporter();
+}
+# [START tracer_start]
+Tracer::start($exporter);
+# [END tracer_start]
+
+function trace_callable()
+{
+    # [START span_with_closure]
+    Tracer::inSpan(
+        ['name' => 'slow_function'],
+        function () {
+            sleep(1);
+        }
+    );
+    # [END span_with_closure]
+}