SilverStripe Hierarchy replacement - Do not traverse into grandchildren in trees.

CustomHierarchy.php

<?php
/**
 * CustomHierarchy
 * 
 * This hierarchy overrides the getChildrenAsUL to not cascade into every child, this makes the sitetree loading a bit
 * snappier
 */
class CustomHierarchy extends Hierarchy {
	
	/**
	 * Returns the children of this DataObject as an XHTML UL.
	 * 
	 * 
	 * @param string $attributes Attributes to add to the UL.
	 * @param string $titleEval PHP code to evaluate to start each child - this should include '<li>'
	 * @param string $extraArg Extra arguments that will be passed on to children, for if they overload this function.
	 * @param boolean $limitToMarked Display only marked children.
	 * @param string $childrenMethod The name of the method used to get children from each object
	 * @param boolean $rootCall Set to true for this first call, and then to false for calls inside the recursion. You should not change this.
	 * @param int $minNodeCount
	 * @return string
	 */
	public function getChildrenAsUL($attributes = "", $titleEval = "", $extraArg = null, $limitToMarked = false, $childrenMethod = "AllChildrenIncludingDeleted", $numChildrenMethod = "numChildren", $rootCall = true, $minNodeCount = 30) {
		if($limitToMarked && $rootCall) {
			$this->markingFinished($numChildrenMethod);
		}
		
		if(!$titleEval) {
			$titleEval = '"<li>" . $child->Title';
		}
		
		$children = $this->owner->$childrenMethod($extraArg);
		
		if(!$children) {
			return '';
		}
		
		if($attributes) {
			$attributes = " $attributes";
		}
		
		$output = '';
		
		foreach($children as $child) {
			if(!$limitToMarked || $child->isMarked()) {
				// Here is the override, only cascade into the child if it's opened.
				if($child->isTreeOpened()) {
					$child->markExpanded();
					$output .= eval("return $titleEval;") . PHP_EOL . $child->getChildrenAsUL('', $titleEval, $extraArg, $limitToMarked, $childrenMethod, $numChildrenMethod, false, $minNodeCount) . "</li>".PHP_EOL;
				} else {
					$output .= eval("return $titleEval;") . "</li>" . PHP_EOL;
				}
				
			}
		}
		return "<ul$attributes>" . PHP_EOL . $output . "</ul>" . PHP_EOL;
	}
	
	/**
	 * Mark a segment of the tree, by calling mark().
	 * 
	 * This method is overrided so it only mark the first children.
	 * 
	 * @return int The actual number of nodes marked.
	 */
	public function markPartialTree($minNodeCount = 1, $context = null, $childrenMethod = "AllChildrenIncludingDeleted", $numChildrenMethod = "numChildren") {
		$minNodeCount =1;
		
		$this->markedNodes = array($this->owner->ID => $this->owner);
		$this->owner->markUnexpanded();
		

		list($id, $node) = each($this->markedNodes);
		$this->markChildren($node, $context, $childrenMethod, $numChildrenMethod);
		return sizeof($this->markedNodes);
	}
}