如何使用PHPExcel从excel文件中删除图像/图像？

Can anybody help to solve this issue, i am new for PHPExcel Libraries, I want to delete image which is on excel file using PHPExcel. I did some code here but i am getting error of

Notice: main(): ArrayIterator::next(): Array was modified outside object and internal position

<?php
    require_once '../Classes/PHPExcel/IOFactory.php';
    require_once '../Classes/PHPExcel.php';        
    $objReader = PHPExcel_IOFactory::createReader('Excel2007');
    $objPHPExcel = $objReader->load(files/test.xlsx);
    $objPHPExcel->setActiveSheetIndex(1);           
    $objPHPExcel = $objPHPExcel->getActiveSheet(1)->getDrawingCollection();
    foreach ($objPHPExcel as $key => $drawing){
        $objPHPExcel->offsetUnset($key);
    }
    $objReader = PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel2007');
    $objReader->save('excel-files/new_test.xlsx');
?>