Do not expect metadata until expecting first read

src/php/lib/Grpc/AbstractCall.php

@@ -47,6 +47,7 @@ abstract class AbstractCall {
   public function __construct(Channel $channel, $method, $deserialize) {
     $this->call = new Call($channel, $method, Timeval::inf_future());
     $this->deserialize = $deserialize;
+    $this->metadata = null;
   }
 
   /**

src/php/lib/Grpc/BidiStreamingCall.php

@@ -43,10 +43,7 @@ class BidiStreamingCall extends AbstractCall {
    * @param array $metadata Metadata to send with the call, if applicable
    */
   public function start($metadata) {
-    $event = $this->call->start_batch([
-        OP_SEND_INITIAL_METADATA => $metadata,
-        OP_RECV_INITIAL_METADATA => true]);
-    $this->metadata = $event->metadata;
+    $this->call->start_batch([OP_SEND_INITIAL_METADATA => $metadata]);
   }
 
   /**
@@ -54,7 +51,14 @@ class BidiStreamingCall extends AbstractCall {
    * @return The next value from the server, or null if there is none
    */
   public function read() {
-    $read_event = $this->call->start_batch([OP_RECV_MESSAGE => true]);
+    $batch = [OP_RECV_MESSAGE => true];
+    if ($this->metadata === null) {
+      $batch[OP_RECV_INITIAL_METADATA] = true;
+    }
+    $read_event = $this->call->start_batch($batch);
+    if ($this->metadata === null) {
+      $this->metadata = $read_event->metadata;
+    }
     return $this->deserializeResponse($read_event->message);
   }
 

src/php/lib/Grpc/ClientStreamingCall.php

@@ -44,10 +44,7 @@ class ClientStreamingCall extends AbstractCall {
    * @param array $metadata Metadata to send with the call, if applicable
    */
   public function start($arg_iter, $metadata = array()) {
-    $event = $this->call->start_batch([
-        OP_SEND_INITIAL_METADATA => $metadata,
-        OP_RECV_INITIAL_METADATA => true]);
-    $this->metadata = $event->metadata;
+    $event = $this->call->start_batch([OP_SEND_INITIAL_METADATA => $metadata]);
     foreach($arg_iter as $arg) {
       $this->call->start_batch([OP_SEND_MESSAGE => $arg->serialize()]);
     }
@@ -60,8 +57,10 @@ class ClientStreamingCall extends AbstractCall {
    */
   public function wait() {
     $event = $this->call->start_batch([
+        OP_RECV_INITIAL_METADATA => true,
         OP_RECV_MESSAGE => true,
         OP_RECV_STATUS_ON_CLIENT => true]);
+    $this->metadata = $event->metadata;
     return array($this->deserializeResponse($event->message), $event->status);
   }
 }