Typo3 page tree flat sorting

sort.php

/**
 * @return array
 */
public function getSortingMatrix(): array
{
    $matrix = [];
    $rootLine = GeneralUtility::makeInstance(RootlineUtility::class, $this->getUid())->get();

    foreach ($rootLine as $level => $item) {
        $matrix[$level] = $item['sorting'];
    }

    return $matrix;
}


/**
 * Sort pages based on sorting and accept tree sorting
 */
\usort($solutions, function ($a, $b) {
    $verdict = 0;
    $aMatrix = $a->getSortingMatrix();
    $bMatrix = $b->getSortingMatrix();

    foreach ($aMatrix as $level => $sorting) {
        if ($sorting === $bMatrix[$level]) {
            continue;
        }
        $verdict = $sorting - $bMatrix[$level];
    }

    return $verdict;
});