Why PHP always gets null values ​​when uploading files

Not long ago, when I was making an extension for the backend of the company's project Guaten.com (http://www.guaten.com/), the product attributes can upload pictures.

I found that the files obtained by the background PHP were always empty. It took me a long time to find out the reason:

Whether PHP can upload files and how many files can be uploaded depends on two things. Values: file_uploads and max_file_uploads.

Found that there are too many tags in the HTML document, exceeding the maximum value set by max_file_uploads in php.ini. Just increase the max_file_uploads.

Original link: http://woqilin.blogspot.com/2016/05/php.html

The above introduces the reason why PHP always gets null values ​​when uploading files, including file upload and PHP content. I hope it will be helpful to friends who are interested in PHP tutorials.