Add sample for functions : Response streaming (GoogleCloudPlatform#1854)

* Add response streaming sample in PHP

* Remove test

* Add unit test

* Add region tags

* Address comments

* lint fix

* fix lint

Author: janell-chen

functions/response_streaming/composer.json

@@ -0,0 +1,6 @@
+{
+    "require": {
+        "google/cloud-functions-framework": "^1.1",
+        "google/cloud-bigquery": "^1.24"
+    }
+}

functions/response_streaming/index.php

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+<?php
+/**
+ * Copyright 2023 Google LLC.
+ *
+ * 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.
+ */
+
+// [START functions_response_streaming]
+use Psr\Http\Message\ServerRequestInterface;
+use Google\Cloud\BigQuery\BigQueryClient;
+
+function streamBigQuery(ServerRequestInterface $request)
+{
+    // Provide the Cloud Project ID by setting env var.
+    $projectId = getenv('GOOGLE_PROJECT_ID');
+    // Example large payload from BigQuery's public dataset.
+    $bigQuery = new BigQueryClient(['projectId' => $projectId]);
+    $queryJobConfig = $bigQuery->query(
+        'SELECT abstract FROM `bigquery-public-data.breathe.bioasq` LIMIT 1000'
+        );
+    $queryResults = $bigQuery->runQuery($queryJobConfig);
+
+    // Stream out large payload by iterating rows and flushing output.
+    foreach ($queryResults as $row) {
+        foreach ($row as $column => $value) {
+            printf('%s' . PHP_EOL, json_encode($value));
+            flush();
+        }
+    }
+    printf('Successfully streamed rows');
+}
+// [END functions_response_streaming]

functions/response_streaming/phpunit.xml.dist

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+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  Copyright 2020 Google LLC
+
+  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.
+-->
+<phpunit bootstrap="../../testing/bootstrap.php" convertWarningsToExceptions="false">
+    <testsuites>
+        <testsuite name="Cloud Functions HTTP Methods Test Suite">
+            <directory>test</directory>
+        </testsuite>
+    </testsuites>
+    <logging>
+        <log type="coverage-clover" target="build/logs/clover.xml"/>
+    </logging>
+    <filter>
+        <whitelist>
+            <directory suffix=".php">.</directory>
+            <exclude>
+              <directory>./vendor</directory>
+            </exclude>
+        </whitelist>
+    </filter>
+</phpunit>

functions/response_streaming/test/UnitTest.php

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+<?php
+/**
+ * Copyright 2023 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.
+ */
+
+/**
+ * For instructions on how to run the samples:
+ *
+ * @see https://github.com/GoogleCloudPlatform/php-docs-samples/tree/main/dlp/README.md
+ */
+declare(strict_types=1);
+
+namespace Google\Cloud\Samples\Functions\ResponseStreaming\Test;
+
+use GuzzleHttp\Psr7\ServerRequest;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Unit tests for the Cloud Function.
+ */
+class UnitTest extends TestCase
+{
+    private static $entryPoint = 'streamBigQuery';
+
+    public static function setUpBeforeClass(): void
+    {
+        require_once __DIR__ . '/../index.php';
+    }
+
+    public function testFunction(): void
+    {
+        $request = new ServerRequest('POST', '/', [], '');
+        ob_start();
+        $this->runFunction(self::$entryPoint, [$request]);
+        $result = ob_get_clean();
+        $this->assertStringContainsString('Successfully streamed rows', $result);
+    }
+
+    private static function runFunction($functionName, array $params = []): void
+    {
+        call_user_func_array($functionName, $params);
+    }
+}