413 Request Entity Too Large using CodeIgniter

It looks like the error is coming not from PHP but from a web server.

If you're using nginx, you could up the max allowed post size with client_max_body_size directive

server {
    ...
    client_max_body_size 128m
    ...
}

If you're using Apache, then there are a couple of options to check for in its config file (httpd.conf).

LimitRequestBody 131072000

If mod_security module is used in Apache, update limit for it as well:

SecRequestBodyLimit 131072000

Don't forget to restart the server.