ViewHelper for merging only if one path is not set ...

DataViewHelper.php

<?php
/**
 * Converts raw flexform xml into an associative array
 *
 */
class Tx_SomeExt_ViewHelpers_DataViewHelper extends Tx_Fluid_Core_ViewHelper_AbstractViewHelper {

	/**
	 * @var array
	 */
	private static $dataCache = array();

	/**
	 * @var Tx_Flux_Service_FluxService
	 */
	protected $configurationService;


	/**
	 * Inject Flux service
	 * @param Tx_Flux_Service_FluxService $configurationService
	 * @return void
	 */
	public function injectConfigurationService(Tx_Flux_Service_FluxService $configurationService) {
		$this->configurationService = $configurationService;
	}

	/**
	 * Render method
	 * @param integer $uid
	 * @param string $path
	 * @throws Tx_Fluid_Core_ViewHelper_Exception
	 * @return array
	 */
	public function render($uid, $path) {
		$table = $this->templateVariableContainer->get('fluxTableName');
		$field = $this->templateVariableContainer->get('fluxRecordField');

		if (TRUE === isset(self::$dataCache[$uid.$table.$field])) {
			return self::$dataCache[$uid.$table.$field];
		}

		$row = $GLOBALS['TYPO3_DB']->exec_SELECTgetSingleRow('uid, pid, is_siteroot,' . $field, $table, sprintf('uid=%d', $uid));

		if (FALSE === $row) {
			throw new Tx_Fluid_Core_ViewHelper_Exception(sprintf('Either table "%s", field "%s" or record with uid %d do not exist.', $table, $field, $uid), 1358679983);
		}


		$dataArray = $this->configurationService->convertFlexFormContentToArray($row[$field]);
		$value = $this->getValue($dataArray, $path);

		if(NULL !== $value) {
			$dataArray = $value;
		}
		else {
			if($row['pid'] > 0 && $row['is_siteroot'] == 0) {
				$dataArray = $this->render($row['pid'], $path);
			}
		}

		self::$dataCache[$uid.$table.$field] = $dataArray;

		return $dataArray;
	}

	protected function getValue($dataArray, $path) {
		if (strpos($path, '.') === FALSE) {
			$value = isset($dataArray[$path]) ? $dataArray[$path] : NULL;
		} else {
			$parts = explode('.', $path);
			$first = array_shift($parts);

			if(isset($dataArray[$first])) {
				$value = Tx_Extbase_Reflection_ObjectAccess::getPropertyPath($dataArray[$first], implode('.', $parts));
			}
		}

		return $value;
	}
}