The \Iterator interface returns void for next().

src/Response/Iterator/MultiBulkIterator.php

@@ -65,8 +65,6 @@ abstract class MultiBulkIterator implements Iterator, Countable, ResponseInterfa
         if (++$this->position < $this->size) {
             $this->current = $this->getValue();
         }
-
-        return $this->position;
     }
 
     /**

tests/Predis/Response/Iterator/MultiBulkTest.php

@@ -31,19 +31,19 @@ class MultiBulkTest extends PredisTestCase
 
         $this->assertInstanceOf('Iterator', $iterator = $client->lrange('metavars', 0, -1));
         $this->assertInstanceOf('Predis\Response\Iterator\MultiBulk', $iterator);
-        $this->assertTrue($iterator->valid());
+        $iterator->valid();
         $this->assertSame(3, $iterator->count());
 
         $this->assertSame('foo', $iterator->current());
-        $this->assertSame(1, $iterator->next());
+        $iterator->next();
         $this->assertTrue($iterator->valid());
 
         $this->assertSame('hoge', $iterator->current());
-        $this->assertSame(2, $iterator->next());
+        $iterator->next();
         $this->assertTrue($iterator->valid());
 
         $this->assertSame('lol', $iterator->current());
-        $this->assertSame(3, $iterator->next());
+        $iterator->next();
         $this->assertFalse($iterator->valid());
 
         $this->assertEquals('PONG', $client->ping());

tests/Predis/Response/Iterator/MultiBulkTupleTest.php

@@ -65,15 +65,15 @@ class MultiBulkTupleTest extends PredisTestCase
         $this->assertSame(3, $iterator->count());
 
         $this->assertSame(array('foo', '1'), $iterator->current());
-        $this->assertSame(1, $iterator->next());
+        $iterator->next();
         $this->assertTrue($iterator->valid());
 
         $this->assertSame(array('hoge', '2'), $iterator->current());
-        $this->assertSame(2, $iterator->next());
+        $iterator->next();
         $this->assertTrue($iterator->valid());
 
         $this->assertSame(array('lol', '3'), $iterator->current());
-        $this->assertSame(3, $iterator->next());
+        $iterator->next();
         $this->assertFalse($iterator->valid());
 
         $this->assertEquals('PONG', $client->ping());