Hi Taufik,
I’m trying to installa ajax plug-in following your instruction but on step 2 I can’t go.
Step 2 : Composer dump-autoload

Next, you need to make sure new function ajax are loaded into current sximo 5.1. 
if you dont have installed composer on your computer , please check this Download Composer 

Autoload New file.

Open your console/terminal then point to your sximo 5 installation . Next , type command as bellow.
    composer dump-autoload
on terminal inside of sximo dir I receive this message:


sh-3.2# composer dump-autoload
sh: composer: command not found

If I use > php composer.phar 
 ______
  / ____/___  ____ ___  ____  ____  ________  _____
 / /   / __ \/ __ `__ \/ __ \/ __ \/ ___/ _ \/ ___/
/ /___/ /_/ / / / / / / /_/ / /_/ (__  )  __/ /
\____/\____/_/ /_/ /_/ .___/\____/____/\___/_/
                    /_/
Composer version 1.4.1 2017-03-10 09:29:45

Usage:
  command [options] [arguments]

Options:
  -h, --help                     Display this help message
  -q, --quiet                    Do not output any message
  -V, --version                  Display this application version
      --ansi                     Force ANSI output
      --no-ansi                  Disable ANSI output
  -n, --no-interaction           Do not ask any interactive question
      --profile                  Display timing and memory usage information
      --no-plugins               Whether to disable plugins.
  -d, --working-dir=WORKING-DIR  If specified, use the given directory as working directory.
  -v|vv|vvv, --verbose           Increase the verbosity of messages: 1 for normal output, 2

composer appare installed.

can you help me?