文件写入（支持var_dump）

方法： 
function output($tip, $fileName = 'success')
{
    $document = $_SERVER['DOCUMENT_ROOT'];
    $newPath = '/uploads/';
    $filePaht = $document. $newPath;
    if (!is_dir($filePaht)) {
        mkdir($filePaht, 0777, true);
    }
    $newFileName = $fileName. '.txt';

    $handle=fopen($filePaht. '/'. $newFileName,"a");
    fwrite($handle,"
-------------------------------------------
");
    fwrite($handle,$tip);
    fwrite($handle,"
-------------------------------------------
");
    fclose($handle);
}
调用：

tip = '测试';

output($tip);
var_dump写入：

ob_start();
var_dump($model->errors, $v);
$result = ob_get_clean();
$this->output($result,'error');