Why is the $_FILES array empty when using PHP to process POST uploads?

When doing a simple form upload test, in the server-side php script, the $_FILES array is empty; so the information uploaded from the browser cannot be obtained. What is the reason?

Through Google, find the following web:

The solution to the empty $_FILES array of PHP upload files

The situation encountered during the test belongs to the first reason described in the article, that is: the attribute enctype="multipart/form-" is not set in the form for uploading files. data".

 The full text is reposted below:

Solution to the empty $_FILES array when uploading files in php:
When using php as an application to upload files, $_FILES is found to be empty when printing in the background Array, this problem may occur for the following two reasons:
Form type reasons or PHP setting issues:
1. Form type:
The form encoding type of the uploaded file must be set to enctype="multipart/form-data", because it needs to be passed For big data, the general submission method is POST.

2. PHP setting problem:
php’s default post_max_size is 2M. If the POST data size is larger than post_max_size, the $_POST and $_FILES super global variables will be empty. The solution is:
1. General file upload, unless the file It is very small. Just like a 5M file, it may take more than a minute to upload. But in PHP, the default maximum execution time of this page is 30 seconds. That is to say, if it exceeds 30 seconds, the script will stop executing. This This leads to the situation that the web page cannot be opened. At this time, we can modify max_execution_time and search for max_execution_time in php.ini. The default is 30 seconds. Change max_execution_time = 0 (the modifiable range is PHP_INI_ALL). 0 means no limit. Or set it in the php file header. ini_set('max_execution_time',0);
2. Modify post_max_size to set the maximum size allowed for POST data. This setting also affects file uploads. Find post_max_size. Change to post_max_size = 150M (the modifiable range is PHP_INI_PHP_INI_PERDIR)
3. Many people will change the second step. But when uploading files, the maximum is still 8M. Why? We also need to change a parameter upload_max_filesize to indicate the uploaded file. The maximum size of the file. Find upload_max_filesize, the default is 8M and change to upload_max_filesize = 100M (the modifiable range is PHP_INI_PHP_INI_PERDIR)
Another thing to note is that post_max_size is the size of the entire expression, and upload_max_filesize is the size of the uploaded file. The former should be larger than the latter.