How to search for keywords in VIM

With VIM pre installed on Mac OS, how to search keywords quickly when editing text?

case $sapi in
  cli)
    php_cli_binary="${exec_prefix}/bin/${program_prefix}php${program_suffix}${exe_extension}"
    ;;
  cgi)
    php_cgi_binary="${exec_prefix}/bin/${program_prefix}php-cgi${program_suffix}${exe_extension}"
    ;;
  esac

In the above file, our goal is to search for keywordsphpAs long as the following operations

1. Press ESC key to quickly return to command mode
2. Input / or?
3. Then enter the keyword PHP and press enter to search
4. Use n to browse the location of the next keyword, and N to browse the previous location