ubuntu 16.04 安裝php5.6

 Ubuntu 16.04默認安裝php7.0環境，但是php7目前兼容性並不是很好，如果自行安裝php5需要清除php7的已安裝包，否則會報錯。

移除默認及已安裝的PHP包

sudo dpkg -l | grep php| awk '{print $2}' |tr "\n" " "
sudo apt-get install aptitude
sudo aptitude purge `dpkg -l | grep php| awk '{print $2}' |tr "\n" " "`

添加 PPA
sudo add-apt-repository ppa:ondrej/php

安裝php5.6
sudo apt-get update
sudo apt-get install php5.6

安裝擴展
sudo apt-get install php5.6-gd
sudo apt-get install php5.6-mysql

安裝Apache2
sudo apt install apache2
sudo apt-get install libapache2-mod-php5.6

安裝MySQL
sudo apt install mysql-server php5.6-mysql    root root0x0
sudo apt-get install mysql-client
mysql_secure_installation

安 phpmyadmin
sudo apt-get install phpmyadmin
sudo apt-get install php5.6-mbstring
sudo apt-get install php5.6-gettext
sudo ln -s /usr/share/phpmyadmin /var/www/html/phpmyadmin

配置phpmyadmin
nano /etc/php/5.6/apache2/php.ini
display_errors = On(顯示錯誤日志，出現兩次，都要改，不然無效)
extension=php_mbstring.dll (開啟mbstring)
sudo dpkg-reconfigure phpmyadmin (重新配置phpmyadmin)