Insert unicode character into Oracle

1. Check & set some database parameters

    select * from nls_database_parameters where parameter like '%SET';

2. Set environment in your PC or your Server (important) 

2.1. Your PC (window) 
- Right click to MyComputer > Properties > Advance system settings > Environment variables > system variables
- Click new, add new variable:
    name: NLS_LANG
    value: AMERICAN_AMERICA.AL32UTF8

- Try to log out/ log in again or restart your PC

2.2. Your linux server
Run command: 
   export NLS_LANG=AMERICAN_AMERICA.AL32UTF8

Or insert this command at the end of   /etc/profile

Configure at the end of file: php/etc/php-fpm.conf 
env[NLS_LANG] = $NLS_LANG

Restart php-fpm