jakoch/phantomjs-installer 2.1.1-p08 requires ext-bz2 * -> the requested PHP extension bz2 is missing from your system.

执行

composer require barryvdh/laravel-debugbar

命令时，提示如下错误

 Problem 1
    - jakoch/phantomjs-installer 2.1.1-p08 requires ext-bz2 * -> the requested PHP extension bz2 is missing from your system.
    - jakoch/phantomjs-installer 2.1.1-p08 requires ext-bz2 * -> the requested PHP extension bz2 is missing from your system.
    - jakoch/phantomjs-installer 2.1.1-p08 requires ext-bz2 * -> the requested PHP extension bz2 is missing from your system.
    - Installation request for jakoch/phantomjs-installer (locked at 2.1.1-p08) -> satisfiable by jakoch/phantomjs-installer[2.1.1-p08].

  To enable extensions, verify that they are enabled in your .ini files

其提示开启bz2扩展，我们只需要在php.ini里将bz2扩展即可（查找bz2去提最前面的;注释即可）