php上传图片

$_files= array("image/jpg","image/jpeg","image/png","image/pjpeg","image/gif","image/bmp","image/x-png");
    if(is_array($_files))
    {
        if(!in_array($_FILES['userfile']['type'],$_files))
        {
            echo "<script>alert('图片类型不符合，请重新上传');history.back();</script>";
            exit;
        }

    }
    if($_FILES['userfile']['error']>0){
        switch($_FILES['userfile']['error']){
            case 1:_alert_back("上传文件超约定的值");
                break;
            case 2:_alert_back("上传文件超约定的值");
                break;
            case 3:_alert_back("部分文件上传");
                break;
            case 4:_alert_back("没有文件上传");
                break;
        }
    exit;

    }
//判断配置大小
if($_FILES['userfile']['size']>2097152){
    _alert_back("超过10000");
}
if(is_uploaded_file($_FILES['userfile']['tmp_name']))
{
    if(!@move_uploaded_file($_FILES['userfile']['tmp_name'],'photo1492310565\'.$_FILES['userfile']['name']))
    {
        _alert_back("移动失败");
    }
    else{
        _alert_back("上传文件成功");
    }

}else{
    _alert_back("上传文件不存在");
}