While it seems that CLI upgrade.php performs enviromental checks (although information on header notes tells it doesn't), it seems that install.php CLI is missing those checks completely.

More yet, it has harcoded one (outdated for Moodle 2.1 and upwards) PHP 5.2.8 condition.

We should enable the environmental checks ASAP, to have it working consistently, surely before proceeding with install_cli_database() or so.

Related: for a list of CLI installer issues: http://tracker.moodle.org/secure/IssueNavigator.jspa?reset=true&jqlQuery=%28summary+%7E+%22%2Bcli+%2Binstall%22+OR+description+%7E+%22%2Bcli+%2Binstall%22+OR+comment+%7E+%22%2Bcli+%2Binstall%22%29+AND+resolution+%3D+Unresolved