Sorting Multi-diminsional array - php

Question

i am trying to sort multi_diminsional array using array_multisort()
but it does nothing to the original array.
here is my code :
foreach ($aOrderArticles as $oOrderArticle) {
$aOrderArticleExportData[$sUserId][$sArticleId]['lastname'] = $oOrder->oxorder__oxbilllname->value;
$aOrderArticleExportData[$sUserId][$sArticleId]['firstname'] = $oOrder->oxorder__oxbillfname->value;
$aOrderArticleExportData[$sUserId][$sArticleId]['title'] = $sTitle;
$aOrderArticleExportData[$sUserId][$sArticleId]['amount'] += $oOrderArticle->oxorderarticles__oxamount->value;
}
$aSortedLastNames = array();
$aSortedFirstNames = array();
foreach($aOrderArticleExportData as $sUserId => $aUserData){
foreach($aUserData as $aArticleData){
$aSortedLastNames [] = $aArticleData ['lastname'];
$aSortedFirstNames [] = $aArticleData ['firstname'];
}
}
array_multisort($aSortedLastNames,SORT_ASC,$aSortedFirstNames,SORT_ASC,$aOrderArticleExportData);

Answer 1

I have fixed the problem by using one foreach loop and getting the current element.
The problem was that some users had more than one article so in our array, we had under same userid more than one record.
That means the number of elements in $aSortedLastNames and $aSortedFirstNames didn't match the number of elements of the main array, that's why array_multisort did not work.
Here is the new loop:
$aSortedNames = array();
foreach ($aOrderArticleExportData as $sUserId => $aUserData) {
$aArticleData = current($aUserData);
$aSortedNames[] = $aArticleData['lastname']. '_' . $aArticleData['firstname'];
}
array_multisort($aSortedNames, SORT_ASC, $aOrderArticleExportData);