问无法在从php调用时使用带身份验证的wget下载文件

EN

#!/bin/bash

if test $# -eq 2
then
    wget -O "$2" $1
elif test $# -eq 4
then
    wget -O "$2" --http-user="$3" --http-password="$4" $1
else
    wget $1
fi

wget -O "$2" --http-user="$3" --http-password="$4" $1 | echo >> output

echo "$3 | $4" >> credentials

if(isset($_POST["startdownload"]))
{
    list($url, $dest, $user, $pass) = explode("|", urldecode($_POST["data"]));
    $filelen = file_len($url);
    $freespace = getRemainingSpace();
    //die( "( Free: $freespace, File: $filelen )" );
    if($filelen > $freespace - 10000)
    {
        $result = json_encode(array("error" => true, 
                        "message" => "There is not enough space to download this file. ( Free: $freespace, File: $filelen )"));
        die($result);
    }
    else
    {
            if($user != "NULL" && $pass != "NULL")
            {
                execInBackground("../dl.sh '{$url}' '../{$dest}' '{$user}' '{$pass}'| at now");
            }
            else
            {
        execInBackground("../dl.sh '{$url}' '../{$dest}' | at now");    
            }
            $result = json_encode(array("error" => false, "message" => "Starting download..."));
            die($result);
    }
}
function execInBackground($cmd) 
{
    if (substr(php_uname(), 0, 7) == "Windows"){
        pclose(popen("start /B ". $cmd, "r")); 
    }
    else {
        exec($cmd . " > /dev/null &");  
    }
}