第58行的system / core / CodeIgniter.php - codeigniter

I would like to run my project on admin directory. my directory:

public_html //installed wordpress
   /admin

on my localhost everything works fine but on my server I got this error message:

Parse error: syntax error, unexpected T_CONST in /home/saanapp/public_html/admin/system/core/CodeIgniter.php on line 58

my config file:

$config['base_url'] = 'http://saanapp.com/admin/';

$config['index_page'] = '';

my .htaccess:

RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php/$1 [L]

permission of admin directory is 755.

my codeigniter version is:

const CI_VERSION = '3.1.5';

my php verson is:

PHP Version 5.2.17

The problem is the version of PHP you are using. Server requirements for CodeIgniter state:

PHP version 5.6 or newer is recommended.

Line 58 of CodeIgniter.php uses the PHP keyword const which was not added to PHP until version 5.3.0 (PHP Docs).

Seems possible that your development server is using a newer version of PHP than the one referenced in your question which is why it worked there but does not on the live server.