Check in php implementation. (#2052)

This pull request includes two implementation: C extension and PHP
package. Both implementations support encode/decode of singular,
repeated and map fields.
diff --git a/php/tests/encode_decode_test.php b/php/tests/encode_decode_test.php
new file mode 100644
index 0000000..d07907c
--- /dev/null
+++ b/php/tests/encode_decode_test.php
@@ -0,0 +1,136 @@
+<?php
+
+require_once('test.pb.php');
+require_once('test_base.php');
+require_once('test_util.php');
+
+use Google\Protobuf\RepeatedField;
+use Google\Protobuf\GPBType;
+use Foo\TestEnum;
+use Foo\TestMessage;
+use Foo\TestMessage_Sub;
+use Foo\TestPackedMessage;
+use Foo\TestUnpackedMessage;
+
+class EncodeDecodeTest extends TestBase
+{
+
+    public function testEncode()
+    {
+        $from = new TestMessage();
+        $this->expectEmptyFields($from);
+        $this->setFields($from);
+        $this->expectFields($from);
+
+        $data = $from->encode();
+        $this->assertSame(TestUtil::getGoldenTestMessage(), $data);
+    }
+
+    public function testDecode()
+    {
+        $to = new TestMessage();
+        $to->decode(TestUtil::getGoldenTestMessage());
+        $this->expectFields($to);
+    }
+
+    public function testEncodeDecode()
+    {
+        $from = new TestMessage();
+        $this->expectEmptyFields($from);
+        $this->setFields($from);
+        $this->expectFields($from);
+
+        $data = $from->encode();
+
+        $to = new TestMessage();
+        $to->decode($data);
+        $this->expectFields($to);
+    }
+
+    public function testEncodeDecodeEmpty()
+    {
+        $from = new TestMessage();
+        $this->expectEmptyFields($from);
+
+        $data = $from->encode();
+
+        $to = new TestMessage();
+        $to->decode($data);
+        $this->expectEmptyFields($to);
+    }
+
+    public function testEncodeDecodeOneof()
+    {
+        $m = new TestMessage();
+
+        $m->setOneofInt32(1);
+        $data = $m->encode();
+        $n = new TestMessage();
+        $n->decode($data);
+        $this->assertSame(1, $n->getOneofInt32());
+
+        $m->setOneofFloat(2.0);
+        $data = $m->encode();
+        $n = new TestMessage();
+        $n->decode($data);
+        $this->assertSame(2.0, $n->getOneofFloat());
+
+        $m->setOneofString('abc');
+        $data = $m->encode();
+        $n = new TestMessage();
+        $n->decode($data);
+        $this->assertSame('abc', $n->getOneofString());
+
+        $sub_m = new TestMessage_Sub();
+        $sub_m->setA(1);
+        $m->setOneofMessage($sub_m);
+        $data = $m->encode();
+        $n = new TestMessage();
+        $n->decode($data);
+        $this->assertSame(1, $n->getOneofMessage()->getA());
+    }
+
+    public function testPackedEncode()
+    {
+        $from = new TestPackedMessage();
+        TestUtil::setTestPackedMessage($from);
+        $this->assertSame(TestUtil::getGoldenTestPackedMessage(),
+                          $from->encode());
+    }
+
+    public function testPackedDecodePacked()
+    {
+        $to = new TestPackedMessage();
+        $to->decode(TestUtil::getGoldenTestPackedMessage());
+        TestUtil::assertTestPackedMessage($to);
+    }
+
+    public function testPackedDecodeUnpacked()
+    {
+        $to = new TestPackedMessage();
+        $to->decode(TestUtil::getGoldenTestUnpackedMessage());
+        TestUtil::assertTestPackedMessage($to);
+    }
+
+    public function testUnpackedEncode()
+    {
+        $from = new TestUnpackedMessage();
+        TestUtil::setTestPackedMessage($from);
+        $this->assertSame(TestUtil::getGoldenTestUnpackedMessage(),
+                          $from->encode());
+    }
+
+    public function testUnpackedDecodePacked()
+    {
+        $to = new TestUnpackedMessage();
+        $to->decode(TestUtil::getGoldenTestPackedMessage());
+        TestUtil::assertTestPackedMessage($to);
+    }
+
+    public function testUnpackedDecodeUnpacked()
+    {
+        $to = new TestUnpackedMessage();
+        $to->decode(TestUtil::getGoldenTestUnpackedMessage());
+        TestUtil::assertTestPackedMessage($to);
+    }
+}