The howsmyssl.com website provides you the option to test the TLS version used by your browser or PHP script. Put the below PHP script on your website document root and access it in a web browser. This will return the TLS version used by your script to connect the remote application.
I have written this in a tls_test.php script and then accessed in a web browser. The result shows the PHP is using TLS 1.2. If your application is using lower version by default, then you can force PHP to use TLS 1.2 with cURL using this tutorial.