Description:
------------
Currently I'm using a custom Streamwrapper for memcached access. The wrapper works 
fine unless I'm using the LOCK_EX parameter for file_put_contents. 

If the parameter is given the function does neither write the file nor calls a 
method of the streamwrapper. I included simple echo statements in all methods of 
the streamwapper but no output is shown. 

I have done this because there is no documentation about which streamwrapper 
methods are called during file_put_contents. I ASSUME that it should call 
stream_lock like flock() does - but as mentioned before there is no output at all.

Test script:
---------------
class MyWrapper { 
   // Assume other methods are implemented

   // Just for demonstration 
   public function stream_lock($operation) {
        echo "I've been called";
    }
}

stream_register_wrapper('myWrapper, 'MyWrapper');
$result = file_put_contents('myWrapper://myFile','content',LOCK_EX);
echo $result; 

Expected result:
----------------
true
(file is written)

Actual result:
--------------
false
(file is not written)