Always use in-memory streams in binary mode for GridFS buffering

src/GridFS/ReadableStream.php

@@ -197,7 +197,7 @@ class ReadableStream
             fclose($this->buffer);
         }
 
-        $this->buffer = fopen("php://temp", "w+");
+        $this->buffer = fopen("php://memory", "w+b");
         $this->bufferEmpty = true;
         $this->bufferFresh = true;
     }

src/GridFS/WritableStream.php

@@ -76,7 +76,7 @@ class WritableStream
 
         $this->chunkSize = $options['chunkSizeBytes'];
         $this->collectionWrapper = $collectionWrapper;
-        $this->buffer = fopen('php://temp', 'w+');
+        $this->buffer = fopen('php://memory', 'w+b');
         $this->ctx = hash_init('md5');
 
         $this->file = [