Php CodeIgniter 2.3无法仅上载PNG文件

JPG的工作很好，PNG的上传失败

我一辈子都不知道为什么

我正在使用CodeIgniter 2.3.2

MIMES.php

'jpg'   =>  array('image/jpeg', 'image/pjpeg'),
'png'   =>  array('image/png', 'image/x-png'),

型号代码：

  $new_file_name = $this->db->insert_id();
  $config['upload_path'] = $_SERVER['DOCUMENT_ROOT'].'/images/mainimg/';
  $config['file_name'] = $new_file_name;
  $config['allowed_types'] = 'png|gif|jpg|jpeg';
  $this->load->library('upload', $config);
  $this->upload->initialize($config);
  if(! $this->upload->do_upload('Image'))
  {
    echo $config['upload_path'] . $this->upload->file_name;
    $errors = $this->upload->display_errors();
    echo $errors;
    exit(-1);
  }

错误：

/Users/Me/Documents/Project/html/images/mainimg/317.png
The filetype you are attempting to upload is not allowed.

---

如果您转储$this->upload->data，您试图上载的文件的文件类型是什么？image/jpeg。。。见鬼@JLeft如果您将此作为答案发布，我将接受。请提供答案的解释允许类型基本上允许上载不同类型的文件，如PNG，只允许上载扩展名为.PNG的文件。同样，其他人。。。。。

$config['allowed_types'] = 'png|gif|jpg|jpeg|pjpeg|x-png'