Chrome / Edge: the install icon in the address bar, or the ⋮ menu then “Install”. Safari on iPhone / iPad: Share⎋ then “Add to Home Screen”. Firefox on a computer does not install web apps. If JumPHP is already installed, Chrome offers “Open in JumPHP” in the address bar: use the ⋮ menu, “Save and share”, “Install page as app” instead.
No ideas yet: suggest yours!