Swift_Mime_SimpleMimeEntity::setChildren PHP Method

    public function setChildren(array $children, $compoundLevel = null)
    {
        // TODO: Try to refactor this logic
        $compoundLevel = isset($compoundLevel) ? $compoundLevel : $this->getCompoundLevel($children);
        $immediateChildren = array();
        $grandchildren = array();
        $newContentType = $this->userContentType;
        foreach ($children as $child) {
            $level = $this->getNeededChildLevel($child, $compoundLevel);
            if (empty($immediateChildren)) {
                //first iteration
                $immediateChildren = array($child);
            } else {
                $nextLevel = $this->getNeededChildLevel($immediateChildren[0], $compoundLevel);
                if ($nextLevel == $level) {
                    $immediateChildren[] = $child;
                } elseif ($level < $nextLevel) {
                    // Re-assign immediateChildren to grandchildren
                    $grandchildren = array_merge($grandchildren, $immediateChildren);
                    // Set new children
                    $immediateChildren = array($child);
                } else {
                    $grandchildren[] = $child;
                }
            }
        }
        if ($immediateChildren) {
            $lowestLevel = $this->getNeededChildLevel($immediateChildren[0], $compoundLevel);
            // Determine which composite media type is needed to accommodate the
            // immediate children
            foreach ($this->compositeRanges as $mediaType => $range) {
                if ($lowestLevel > $range[0] && $lowestLevel <= $range[1]) {
                    $newContentType = $mediaType;
                    break;
                }
            }
            // Put any grandchildren in a subpart
            if (!empty($grandchildren)) {
                $subentity = $this->createChild();
                $subentity->setNestingLevel($lowestLevel);
                $subentity->setChildren($grandchildren, $compoundLevel);
                array_unshift($immediateChildren, $subentity);
            }
        }
        $this->immediateChildren = $immediateChildren;
        $this->children = $children;
        $this->setContentTypeInHeaders($newContentType);
        $this->fixHeaders();
        $this->sortChildren();
        return $this;
    }