PHP cannot find .net assembly in the .net-4 GAC

Question

<?php

$console = new DOTNET("ProjectX.Core, Version=1.0.0.0, Culture=neutral, PublicKeyToken=KeyTokenHere-i used a real value here", "ProjectX.Core.Services.ServicX");

echo '1';

?>

The error message:

Fatal error: Uncaught exception 'com_exception' with message 'Failed to instantiate .Net object [CreateInstance] [0x80070002] The system cannot find the file specified.

What's the problem can be?