php禁止用下载工具来下载文件

    <?php        
    if(strpos($_SERVER["HTTP_USER_AGENT"],"MSIE 8.0"))        
    echo "Internet Explorer 8.0"; // 这里可以写其他的执行命令        
    else if(strpos($_SERVER["HTTP_USER_AGENT"],"MSIE 7.0"))        
    echo "Internet Explorer 7.0";        
    else if(strpos($_SERVER["HTTP_USER_AGENT"],"MSIE 6.0"))        
    echo "Internet Explorer 6.0";     
    else if(strpos($_SERVER["HTTP_USER_AGENT"],"Firefox/3"))        
    echo "Firefox 3";        
    else if(strpos($_SERVER["HTTP_USER_AGENT"],"Firefox/2"))        
    echo "Firefox 2";        
    else if(strpos($_SERVER["HTTP_USER_AGENT"],"Chrome"))        
    echo "Google Chrome";        
    else if(strpos($_SERVER["HTTP_USER_AGENT"],"Safari"))        
    echo "Safari";        
    else if(strpos($_SERVER["HTTP_USER_AGENT"],"Opera"))        
    echo "Opera";        
    else echo $_SERVER["HTTP_USER_AGENT"];     
    ?>  

    <?php  
    if(strpos($_SERVER["HTTP_USER_AGENT"],"MSIE"))echo"禁止用IE浏览器或其他下载工具下载";  
    else header("Content-Disposition: attachment; filename='jquery.js'");//写上文件名  
    ?>