sudo apt update
   sudo apt upgrade virtualbox
   sudo apt upgrade virtualbox-source
   sudo m-a prepare
   sudo m-a a-i virtualbox-source 
   sudo apt-get autoremove 

 sudo LC_ALL=C.UTF-8 add-apt-repository ppa:ondrej/php                                                                                                       │                          
                         │                                                                                                                                                             │                          
                         │ sudo apt-get update                                                                                                                                         │                          
                         │                                                                                                                                                             │                          
                         │ And the install correct PHP version:                                                                                                                        │                          
                         │                                                                                                                                                             │                          
                         │ sudo apt-get install php7.0 # for PHP 7.0                                                                                                                   │                          
                         │                                                                                                                                                             │                          
                         │ sudo apt-get install php5.6 # for PHP 5.6                                                                                                                   │                          
                         │                                                                                                                                                             │                          
                         │ sudo apt-get install php5.5 # for PHP 5.5                                                                                                                   │                          
                         │                                                                                                                                                             │                          
                         │ The packages for extensions contain modules for all supported PHP versions and can be installed with (f.e. xdebug and APCu):                                │                          
                         │                                                                                                                                                             │                          
                         │ sudo apt-get install php-xdebug php-apcu 