Fatal error: Call to a member function on a non-object

[prajataayu123]

Can anyone please guide me as to how to fix the below mentioned problem from php

...
Fatal error: Call to a member function on a non-object in /usr/local/apache2/htdocs/knowledgeTree-OSS/lib/browse/DocumentCollect ion.inc.php on line 414


/////////////////

The code is as follows...
[code=php]
function setSorting() {
387
388 $this->_sorted = true;
389
390 // defaults
391 $this->_sDocumentSort Field = 'DM.name';
392 $this->_sFolderSortFi eld = 'F.name';
393
394 foreach ($this->columns as $key => $oColumn) {
395 if ($oColumn->namespace == $this->sort_column) {
396 $this->columns[$key]->setSortedOn(tr ue);
397 $this->columns[$key]->setSortDirecti on($this->sort_order);
398
399 // get the join params from the object.
400 $aFQ = $this->columns[$key]->addToFolderQue ry();
401 $aDQ = $this->columns[$key]->addToDocumentQ uery();
402
403 $this->_sFolderJoinCl ause = $aFQ[0];
404 $this->_aFolderJoinPa rams = $aFQ[1];
405
406 if ($aFQ[2]) { $this->_sFolderSortFi eld = $aFQ[2]; }
407 $this->_sDocumentJoin Clause = $aDQ[0];
408 $this->_aDocumentJoin Params = $aDQ[1];
409
410 if ($aDQ[2]) {
411 $this->_sDocumentSort Field = $aDQ[2]; }
412 } else {
413 /* $oColumn->setSortedOn(fa lse);*/
414 $oColumn->setSortedOn(fa lse);
415 }
416 }
[/code]
The problem is at line 414

[code green]

You need to pass this object into your function

$oColumn