在 Ubuntu 服务器设置期间，我需要启用 php 作为 apache2 模块。我试过跑步sudo a2enmod php5，但它回来了ERROR: Module php5 does not exist!
经过一番搜索，我偶然发现了 gerard 的这个提示：
如果 sudo a2enmod php5 返回“$ 这个模块不存在！”，您应该清除（而不只是删除）libapache2-mod-php5 包并重新安装它。请务必在再次测试您的网站之前清除浏览器的缓存。”
然而，运行sudo apt-get --purge remove libapache2-mod-php5，返回Package libapache2-mod-php5 is not installed, so not removed。自然，我尝试使用 安装它sudo apt-get install libapache2-mod-php5，但后来我得到：
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies.
libapache2-mod-php5 : Depends: libxml2 (>= 2.8.0) but 2.7.8.dfsg-5.1ubuntu4.6 is to be installed
Recommends: php5-cli but it is not going to be installed
E: Unable to correct problems, you have held broken packages.
我试图更新 && upgrade 希望libxml2能得到更新，但没有发生。我也尝试安装 php5-cli，但得到：
The following packages have unmet dependencies.
php5-cli : Depends: libxml2 (>= 2.8.0) but 2.7.8.dfsg-5.1ubuntu4.6 is to be installed
Depends: libedit2 (>= 2.11-20080614-4) but 2.11-20080614-3ubuntu2 is to be installed
E: Unable to correct problems, you have held broken packages.
在这一点上，我迷路了。运行 php -v，表示 php 正在运行，但是：
PHP 5.4.17 (cli) (built: Aug 7 2013 11:40:38)
Copyright (c) 1997-2013 The PHP Group
Zend Engine v2.4.0, Copyright (c) 1998-2013 Zend Technologies