custom tree menu into sidebar

hi all,

I am just trying to build my own customized wordpress tree menu, starting from the post where the user is and recursively querying the db via $wpdb to obtain a full category tree, until it reaches the top-level categories.

The question is this: it appears that every turn that i do in the cycle, the variable $treeContent ( or in the previous version, the array $theTree, appears to empty himself, despite I declare it out of the cycling function. Can somone explain me how I can solve this problem?

I had posted the code here It is thrown directly on the top of the sidebar.php file into my theme folder. Later I will build the complete plugin. Please have a look.
Many thanks,

Luca

——- START CODE EXCERPT ——–

<?php
		$theTree = array();
		$treeContent = '';

		function printContentNode($inputId) {
			global $wpdb;

			//$layerArray = array(); //creo array per il layer -- da appendere a $theTree;
			$rowList = '';
			//echo "elenco quelli sullo stesso livello<br />";
			$rowList .=  "<!--inizio giro: " . $inputId . "-->";

			//query di selezione stesso livello -- stesso parent ($parentId);
			$rows = $wpdb->get_results("
			SELECT name AS catName,
			term_taxonomy_id AS catId,
			parent AS catParent
			FROM wp_terms LEFT JOIN wp_term_taxonomy
			ON wp_terms.term_id = wp_term_taxonomy.term_id
			WHERE wp_term_taxonomy.parent = " . $inputId . "
			;");
			$subLayerArray = array();
			foreach ($rows as $row) {
				// doppio giro per estrarre gli item dagli oggetti
				//che il metodo di wpdb crea di default;
				foreach ($row as $rowKey => $rowItem) {
					//echo " // rowItem (" . $rowKey . ") " . $rowItem;
					$subLayerArray[$rowKey] = $rowItem;
				}
				/*
				echo "<br /><br />subLayer: ";
				print_r($subLayerArray);
				echo "<br /><br />";
				*/
				$layerArray[] = $subLayerArray; // same as array_push();
				$rowList .= '<li><a href="' . $_SERVER['PHP_SELF'] . '?cat=' . $subLayerArray['catId'] . '">' . $subLayerArray['catName'] . '</a></li>';
			}

			//echo "<br />";
			$rowList = '<ul>' . $rowList . '</ul>';
			return $rowList;
		}

		function printParentNode($inputId) {
			global $wpdb;

			//echo "estraggo il parente<br />";
			$theParent = $wpdb->get_results("
			SELECT name AS catName,
			term_taxonomy_id AS catId,
			parent AS catParent
			FROM wp_terms LEFT JOIN wp_term_taxonomy
			ON wp_terms.term_id = wp_term_taxonomy.term_id
			WHERE wp_terms.term_id = " . $inputId . "
			;");
			/*
			print_r($theParent);
			echo "<br /><br />";
			*/
			//$newParentId = $theParent[0]->catParent;
			//$layerArray["mainParent"] = $theParent[0]->catName;
			/*
			echo "<br /><br />layer(" . $parentId . "): ";
			print_r($layerArray);
			echo "<br /><br />";

			array_unshift($theTree, $layerArray);
			*/
			$subArray = array();
			foreach ($theParent[0] as $theKey => $theItem) {
				$subArray[$theKey] = $theItem;
			}
			return $subArray;
		}

		function printLayer($parentId) {

			global $wpdb; // fix al problema dell'oggetto non trovato
			//vedi link -> http://wordpress.org/support/topic/240236

			$levelOutput = printContentNode($parentId);

			echo "pre: " . $treeContent . "<br />";
			$treeContent = $levelOutput . $treeContent;
			echo "all: " . $treeContent;
			//echo '<ul>' . $rowList . '</ul>';
			//echo "<!--fine giro: " . $parentId . "-->";
			if ($parentId != 0) { // ricorsiva;

				$levelParent = printParentNode($parentId);
				print_r($levelParent);
				echo "theP: " . $levelParent['catParent'].'<br />';
				printLayer($levelParent['catParent']);
			} else { // arrivato a livello zero;

				/*
				echo "<br /><br />layer(" . $parentId . "): ";
				print_r($layerArray);
				echo "<br /><br />";
				array_unshift($theTree, $layerArray);
				*/
			}
		}
		if (is_category() || is_single()) {
			echo "cat caso 1<br />";
			$myCats = get_the_category();
		} else {
			echo "cat caso 2<br />";
			$myCats = get_the_category(0);
		}
		if (count($myCats) == 1) {
			$curCat = $myCats[0];
			echo "categoria parente singola (" . $curCat->name . " :: " . $curCat->parent . ")<br />";
			print_r($curCat);
			echo "<br />";
			//echo "<br /> / " . $curCat->parent . " / <br />";

			printLayer($curCat->parent);//primo giro di lancio, poi ricorsiva;
			//$result .= '<ul class ="custom_menu">';
			//$result .= $treeContent;
			//$result .= '</ul>';
		} else {
			echo "errore! questo post ha piu parenti";
		}
		?>

——– END CODE EXCERPT ——–