PR #3447 introduced a new class JInstallerScript which allows to specify a minimum PHP and Joomla version for extensions by simply setting the respective property in the extensions script file (assuming it extends that class).
The check is done during the preflight stage.

Summary of Changes

• Changing those checks so they actually return false if the minimum requirement fails, aborting the installation with an error message. Currently it just shows the warning but the extensions still installs.
• Changing the version check so it is indeed a minimum requirement. Currently the specified minimum version is considered "to low".

Testing Instructions

If you have an extension already using those features, test that it works as expected. Adjust the minimum versions and check that installation succeeds/fails as expected.

Expected result

If the installation doesn't meet the minimum requirements, the extension should not install.
If the installation meets exactly the minimum requirements, the extension should install without any message.

Actual result

Installation isn't aborted at all and if the minimum requirement is met exactly, the message is still shown.

Documentation Changes Required

None

Pinging @wilsonge since he was the original writer of those lines.