Installing php-dev results in 7.0 packages being installed instead of 7.3

Question

When I run -

apt-get install php-dev

I see a bunch of php 7.0 packages being installed -

The following additional packages will be installed: dh-php libexporter-tiny-perl liblist-moreutils-perl libssl-dev libssl-doc php7.0-cli php7.0-common php7.0-dev php7.0-json php7.0-opcache php7.0-readline pkg-php-tools shtool zlib1g-dev

But I definitely have php 7.3 installed -

php -v PHP 7.3.1-1+ubuntu16.04.1+deb.sury.org+1 (cli) (built: Jan 13 2019 10:19:01) ( NTS )

How can I debug my system to figure out why php-dev is trying to install the older version of these packages? I want the 7.3 version of phpize to be installed but instead the 7.0 version is installed.

Ubuntu version - Ubuntu 16.04.6 LTS

I tried to understand how php-dev tries to figure out which version of php is installed on the machine, but I couldn't find any docs to that end.

Answer 1

php-dev is a dependency package:

apt depends php-dev

php-dev
  Depends: php7.4-dev

If you issue the command, I would expect you will see the dependency to php7.0-dev.

Perhaps you installed your php by a third party installation like xampp. Such installations do not magically integate in the repository but stay isolated.

If you are lucky, you can find the package php7.3-dev in the repository and can install it directly via

apt install php7.3-dev`

Else you have to take the installation path that you used to get php 7.3.

BTW: You are aware, that Ubuntu 16.04 LTS is not supported anymore and also PHP 7.x is not supported anymore by PHP.net?