It is quite easy to find PHP version installed on your web-server.
X.X in ioncube_loader_lin_X.X.so is PHP version installed on your server.
1) Simply write a line of code: <?php echo phpinfo(); ?> and save as info.php
2) Upload this file in root folder of your website and run from browser Ex: https://www.yourwebsite.com/info.php
3) This will show you Latest PHP version installed on your server.
4) If version is 5.2.6 then replace only first two digits with X.X so it would be like:
Save as php.ini (if version is 4.0.x) OR php5.ini (if version is 5.x.x) and upload it on website root folder.
NOTE: Make sure /ioncube/ioncube_loader_lin_5.2.so should be available in root folder.