protected function checkIfSingleSysFolderNotEmpty(
        $fieldName,
        $canUseFlexforms,
        $sheet,
        $explanation
    ) {
        $this->checkIfPositiveInteger(
            $fieldName,
            $canUseFlexforms,
            $sheet,
            $explanation
        );
        $this->checkIfSysFoldersOrEmpty(
            $fieldName,
            $canUseFlexforms,
            $sheet,
            $explanation
        );
    }
protected function checkIfSingleSysFolderNotEmpty(
        $fieldName,
        $canUseFlexforms,
        $sheet,
        $explanation
    ) {
        $this->checkIfPositiveInteger(
            $fieldName,
            $canUseFlexforms,
            $sheet,
            $explanation
        );
        $this->checkIfSysFoldersOrEmpty(
            $fieldName,
            $canUseFlexforms,
            $sheet,
            $explanation
        );
    }
protected function checkIfSingleSysFolderNotEmpty ( $ fieldName , $ canUseFlexforms , $ sheet , $ explanation ) { $ this -> checkIfPositiveInteger ( $ fieldName , $ canUseFlexforms , $ sheet , $ explanation ) ; $ this -> checkIfSysFoldersOrEmpty ( $ fieldName , $ canUseFlexforms , $ sheet , $ explanation ) ; }
Checks whether a configuration value is non-empty and contains a
single system folder PID.

@param string $fieldName
TS setup field name to extract, must not be empty
@param bool $canUseFlexforms
whether the value can also be set via flexforms (this will be
mentioned in the error message)
@param string $sheet
flexforms sheet pointer, eg. "sDEF", will be ignored if
$canUseFlexforms is set to FALSE
@param string $explanation
a sentence explaining what that configuration value is needed for,
must not be empty

@return void
Checks whether a configuration value is non - empty and contains a single system folder PID .