//无法解析php文件，浏览器提示下载所要打开的php文件
执行：
sudo apt-get install libapache2-mod-php5
sudo a2enmod php5
如果显示为：
This module does not exist!
那就要彻底删除libapache2-mod-php5，然后重新安装它
sudo apt-get remove --purge libapache2-mod-php5
sudo apt-get install libapache2-mod-php5
重启apache2
sudo /etc/init.d/apache2 restart
清除浏览器缓存，然后输入http:localhost
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apache 和 命令行的php 用的不是一个php.ini配置文件
php -ini | grep extension 搜索扩展文件库
sudo apt-get install php5-mcrypt
sudo apt-get install php5-mysql
sudo apt-get install php5.6-curl
sudo apt-get install php5.6-fpm php5.6-mysql php5.6-common php5.6-curl php5.6-cli php5.6-mcrypt php5.6-mbstring php5.6-dom
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安装xdebug
（最开始安装xdebug2.1出现编译错误，换用一个高版本的2.4: )
tar -zxvf xdebug-2.4.0.tgz -C Xbug2.4 #解压到Xbug2.4
cd Xbud2.4
cd ./Xbug2.4
cd xdebug-2.4.0
sudo apt-get install php7.0-dev
phpize
make ./configure
sudo ./configure
sudo make
make test
sudo make install
sudo cp ~/Downloads/Xbug2.4/xdebug-2.4.0/modules/xdebug.so /usr/lib/php/7.0/
sudo gedit /etc/php/7.0/apache2/php.ini #配置php.ini
https://xdebug.org/download.php
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Ubuntu下安装php的gd,mysql扩展库
# apt-get install php5-gd
# apt-get install php5-mysql