php system 调用命令压缩文件

function addZip($webdocs, $zipfile, $param, $file){
    system("cd $webdocs; tar $param $zipfile \"".$file ."\"",$output);    
   if ($output == 0){
       echo " OK\r\n";    
       return 0;
   }else {
       echo " Fail:".(int)$output."\r\rn";
       return -1;
   }
}

$zipfile = "/root/admintool_zip_resources_$date.tar.gz";
$webdocs = "/webdocs";        
$isfirst = true;

if ($isfirst == true){
    $isfirst = false;
    addZip($webdocs, $zipfile, "cf", trim($val[‘resource_links‘]));                
}else {
    addZip($webdocs, $zipfile, "rf", trim($val[‘resource_links‘]));                
}