UpgradeTool::checkVersion PHP Method

    function checkVersion($versionInfo, $displayInfo = false)
    {
        if (!$versionInfo) {
            $application = PKPApplication::getApplication();
            printf("Failed to load version info from %s\n", $application->getVersionDescriptorUrl());
            exit(1);
        }
        $dbVersion = VersionCheck::getCurrentDBVersion();
        $codeVersion = VersionCheck::getCurrentCodeVersion();
        $latestVersion = $versionInfo['version'];
        printf("Code version:      %s\n", $codeVersion->getVersionString(false));
        printf("Database version:  %s\n", $dbVersion->getVersionString(false));
        printf("Latest version:    %s\n", $latestVersion->getVersionString(false));
        $compare1 = $codeVersion->compare($latestVersion);
        $compare2 = $dbVersion->compare($codeVersion);
        if (!$displayInfo) {
            if ($compare2 < 0) {
                printf("Database version is older than code version\n");
                printf("Run \"{$this->scriptName} upgrade\" to update\n");
                exit(0);
            } else {
                if ($compare2 > 0) {
                    printf("Database version is newer than code version!\n");
                    exit(1);
                } else {
                    if ($compare1 == 0) {
                        printf("Your system is up-to-date\n");
                    } else {
                        if ($compare1 < 0) {
                            printf("A newer version is available:\n");
                            $displayInfo = true;
                        } else {
                            printf("Current version is newer than latest!\n");
                            exit(1);
                        }
                    }
                }
            }
        }
        if ($displayInfo) {
            printf("         tag:     %s\n", $versionInfo['tag']);
            printf("         date:    %s\n", $versionInfo['date']);
            printf("         info:    %s\n", $versionInfo['info']);
            printf("         package: %s\n", $versionInfo['package']);
        }
        return $compare1;
    }