protected function checkRequirements()
{
$this->checkPhpVersion();
$this->checkPhpExtensions();
$this->checkPhpIniSettings();
$this->checkAvailableFunctions();
$this->checkSubFolder();
$this->checkFilePermissions();
$this->checkAvailableFiles();
$this->checkApacheRewrites();
// error status
return !$this->hasErrors() && !$this->hasWarnings();
}