I migrated Prestashop from localhost to website domain using digitalocean, but when I open this website I get this error
Fatal error: Uncaught --> Smarty: unable to write file /var/www/html/prestashop/cache/smarty/compile/a4/36/f1/wrt549a35e49b3b44_77591243 <-- thrown in /var/www/html/prestashop/tools/smarty/sysplugins/smarty_internal_write_file.php on line 46.
I tried to change permissions on the smarty folder to 755, but it didn't work. I don't know how to fix it.
You problem is definitely about permissions. It depends on how Apache and PHP are set up.
First, check who owns the folders. For example, simple apache2 and php installation runs as www-data user. For example, if you connected to FTP with 'user1' and uploaded your files there, then the files are owned by you. The group is probably also set to 'user1'.
Therefore, you can modify, write the files, but PHP processes cannot, because they dont own the files (PHP runs as www-data, for example).
Your best bet is to contact server administrator and ask him to help you out.
Rememeber: never set 777 for any files/folders on a website, solve the problem the correct way.