NTS
means Not-Thread-Safe, information on PHP's Thread Safety feature can be found here.
From the question I linked:
A Thread Safe version should be used if you install PHP as an Apache
module, as a Worker MPM (multi-processing model).
The Non Thread Safe version should be used if you install PHP as a CGI
binary.
You need to find out whether your PHP installation is thread-safe, to do so:
- Navigate to your PHP Info page (if you do not have one, create a PHP file with
<?php phpinfo(); ?>
.
- Load the page, and look for the Thread Safety line; if enabled it will say
Enabled
(or True
on some installations).
If Thread Safety is enabled, you must use the thread safe version of the extension, which in your case is Phalcon 1.3.4 - Windows x64 for PHP 5.5.0 (VC11)
.