How to Change the Default Version of PHP (7.2) on Ubuntu 19.04

Change the default version of php 7.2 On Ubuntu 19.04

Update the apt repository by executing the following command

root@linuxhelp:~# apt update
Hit:1 http://security.ubuntu.com/ubuntu disco-security InRelease
Hit:2 http://in.archive.ubuntu.com/ubuntu disco InRelease
Hit:3 http://in.archive.ubuntu.com/ubuntu disco-updates InRelease
Hit:4 http://in.archive.ubuntu.com/ubuntu disco-backports InRelease
Reading package lists... Done
Building dependency tree       
Reading state information... Done
132 packages can be upgraded. Run 'apt list --upgradable' to see them.

Add the repository to install the different versions of php

root@linuxhelp:~# add-apt-repository ppa:ondrej/php
 Co-installable PHP versions: PHP 5.6, PHP 7.x and most requested extensions are included. Only Supported Versions of PHP (http://php.net/supported-versions.php) for Supported Ubuntu Releases (https://wiki.ubuntu.com/Releases) are provided. Don't ask for end-of-life PHP versions or Ubuntu release, they won't be provided.

Debian oldstable and stable packages are provided as well: https://deb.sury.org/#debian-dpa

You can get more information about the packages at https://deb.sury.org

BUGS&FEATURES: This PPA now has a issue tracker:
https://deb.sury.org/#bug-reporting

CAVEATS:
1. If you are using php-gearman, you need to add ppa:ondrej/pkg-gearman
2. If you are using apache2, you are advised to add ppa:ondrej/apache2
3. If you are using nginx, you are advise to add ppa:ondrej/nginx-mainline
   or ppa:ondrej/nginx

PLEASE READ: If you like my work and want to give me a little motivation, please consider donating regularly: https://donate.sury.org/

WARNING: add-apt-repository is broken with non-UTF-8 locales, see 
https://github.com/oerdnj/deb.sury.org/issues/56 for workaround:

#LC_ALL=C.UTF-8 add-apt-repository ppa:ondrej/php
 More info: https://launchpad.net/~ondrej/+archive/ubuntu/php
Press [ENTER] to continue or Ctrl-c to cancel adding it.

Hit:1 http://in.archive.ubuntu.com/ubuntu disco InRelease
Hit:2 http://security.ubuntu.com/ubuntu disco-security InRelease
Hit:3 http://in.archive.ubuntu.com/ubuntu disco-updates InRelease
Get:4 http://ppa.launchpad.net/ondrej/php/ubuntu disco InRelease [20.8 kB]
Hit:5 http://in.archive.ubuntu.com/ubuntu disco-backports InRelease
Get:6 http://ppa.launchpad.net/ondrej/php/ubuntu disco/main amd64 Packages [37.5 kB]
Get:7 http://ppa.launchpad.net/ondrej/php/ubuntu disco/main i386 Packages [37.5 kB]
Get:8 http://ppa.launchpad.net/ondrej/php/ubuntu disco/main Translation-en [16.8 kB]
Fetched 113 kB in 3s (43.9 kB/s)          
Reading package lists... Done

Check the default version of php

root@linuxhelp:~# php -v
PHP 7.2.17-0ubuntu0.19.04.1 (cli) (built: Apr 18 2019 18:01:25) ( NTS )
Copyright (c) 1997-2018 The PHP Group
Zend Engine v3.2.0, Copyright (c) 1998-2018 Zend Technologies
    with Zend OPcache v7.2.17-0ubuntu0.19.04.1, Copyright (c) 1999-2018, by Zend Technologies

Install the php version 5.6 as follows

root@linuxhelp:~# apt install php5.6 -y
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following additional packages will be installed:
  libapache2-mod-php5.6 php5.6-cli php5.6-common php5.6-json php5.6-opcache php5.6-readline
The following NEW packages will be installed:
  libapache2-mod-php5.6 php5.6 php5.6-cli php5.6-common php5.6-json php5.6-opcache php5.6-readline
0 upgraded, 7 newly installed, 0 to remove and 160 not upgraded.
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.
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libapache2-mod-php5.6: php7.2 module already enabled, not enabling PHP 5.6
Setting up php5.6 (5.6.40-8+ubuntu19.04.1+deb.sury.org+1) ...
Processing triggers for man-db (2.8.5-2) ...

Install the required modules of php5.6 in the below given way.

root@linuxhelp:~# apt install php5.6-mysql php5.6-simplexml php5.6-gd php5.6-mcrypt -y
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Note, selecting 'php5.6-xml' instead of 'php5.6-simplexml'
php5.6-mcrypt is already the newest version (5.6.40-8+ubuntu19.04.1+deb.sury.org+1).
.
.
.
Creating config file /etc/php/5.6/mods-available/xsl.ini with new version
Setting up php5.6-gd (5.6.40-8+ubuntu19.04.1+deb.sury.org+1) ...

Creating config file /etc/php/5.6/mods-available/gd.ini with new version

Processing triggers for libapache2-mod-php5.6 (5.6.40-8+ubuntu19.04.1+deb.sury.org+1) ...

Install another php version 7.0 as follows:

root@linuxhelp:~# apt install php7.0 -y
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following additional packages will be installed:
  libapache2-mod-php7.0 php7.0-cli php7.0-common php7.0-json php7.0-opcache php7.0-readline
The following NEW packages will be installed:
  libapache2-mod-php7.0 php7.0 php7.0-cli php7.0-common php7.0-json php7.0-opcache php7.0-readline
0 upgraded, 7 newly installed, 0 to remove and 160 not upgraded.
Need to get 3,669 kB of archives.
After this operation, 14.2 MB of additional disk space will be used.
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.
.
.
.
Creating config file /etc/php/7.0/cli/php.ini with new version
Setting up libapache2-mod-php7.0 (7.0.33-8+ubuntu19.04.1+deb.sury.org+1) ...

Creating config file /etc/php/7.0/apache2/php.ini with new version
libapache2-mod-php7.0: php7.2 module already enabled, not enabling PHP 7.0
Setting up php7.0 (7.0.33-8+ubuntu19.04.1+deb.sury.org+1) ...
Processing triggers for man-db (2.8.5-2) ...

Install the php modules of 7.0 version by executing the following command.

root@linuxhelp:~# apt install php7.0-mysql php7.0-simplexml php7.0-gd php7.0-mcrypt -y
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Note, selecting 'php7.0-xml' instead of 'php7.0-simplexml'
The following NEW packages will be installed:
  php7.0-gd php7.0-mcrypt php7.0-mysql php7.0-xml
0 upgraded, 4 newly installed, 0 to remove and 160 not upgraded.
Need to get 289 kB of archives.
After this operation, 1,240 kB of additional disk space will be used.
Get:1 http://ppa.launchpad.net/ondrej/php/ubuntu disco/main amd64 php7.0-gd amd64 7.0.33-8+ubuntu19.04.1+deb.sury.org+1 [28.3 kB]
.
.
.
.
Creating config file /etc/php/7.0/mods-available/mysqlnd.ini with new version

Creating config file /etc/php/7.0/mods-available/mysqli.ini with new version

Creating config file /etc/php/7.0/mods-available/pdo_mysql.ini with new version
Processing triggers for libapache2-mod-php7.0 (7.0.33-8+ubuntu19.04.1+deb.sury.org+1) ...

Now lets check the version of php after the installation of two php versions 5.6 and 7.0

root@linuxhelp:~# php -v
PHP 7.2.17-0ubuntu0.19.04.1 (cli) (built: Apr 18 2019 18:01:25) ( NTS )
Copyright (c) 1997-2018 The PHP Group
Zend Engine v3.2.0, Copyright (c) 1998-2018 Zend Technologies
    with Zend OPcache v7.2.17-0ubuntu0.19.04.1, Copyright (c) 1999-2018, by Zend Technologies

Set the default versions of php as 5.6 by using alternatives utility .

root@linuxhelp:~# update-alternatives --set php /usr/bin/php5.6
update-alternatives: using /usr/bin/php5.6 to provide /usr/bin/php (php) in manual mode

Check the default version of php after setting.

root@linuxhelp:~# php -v
PHP 5.6.40-8+ubuntu19.04.1+deb.sury.org+1 (cli) 
Copyright (c) 1997-2016 The PHP Group
Zend Engine v2.6.0, Copyright (c) 1998-2016 Zend Technologies
    with Zend OPcache v7.0.6-dev, Copyright (c) 1999-2016, by Zend Technologies

With this,Default php version 7.2 On Ubuntu 19.04 has been changed successfully .