Script to compile php 7.2 on Slackware 14.2 Installation
cd /tmp
git clone https://github.com/redscience/php7.2-Slackware-build.git
cd php7.2-Slackware-build
chmod +x ./php7Build.sh
./php7Build.sh
Assuming everything happened according to plan (the compile finished without errors), the finished package should be in the directory declared as "OUTPUT" in the SlackBuild script (this defaults to the /tmp directory). Use installpkg to install it; you'll probably want to move it to some other location for safekeeping after it's installed.
Enjoy