php xls如何转csv

<?php 
    header("Content-Type:text/html;charset=utf-8");
    require_once 'PHPExcel/PHPExcel.php'; 
    $d = dir('xls/');
        while (($file = $d->read()) !== false){
            if(substr(strrchr($file, '.'), 1) == 'xls'){
                $arr[] = $file; 
            }
        }
    //把所有xls文件列出列表，勾选提交到这边$_POST
        foreach($_POST as $k => $item){
            foreach($item as $v){
                //只获取文件名
                $file = str_replace('.xls','',$arr[$v]);
                getCsv($file);
            }
        }
    function getCsv($file){
        $filename = "xls/".$file.".xls";
        $objReader = new PHPExcel_Reader_Excel5();
        //$objReader = PHPExcel_IOFactory::createReader('Excel5');
        $objPHPExcel = $objReader->load($filename);
        //$objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'CSV');
        $objWriter = new PHPExcel_Writer_CSV($objPHPExcel);
        $objWriter->save(str_replace('.xls', '.csv',$filename));
        $root = "xls/".$file.".csv";
        $newRoot='csv/'.$file.'.csv'; //新目录
        copy($root,$newRoot); //拷贝到新目录
        unlink($root); //删除旧目录下的文件
    } 
?>