With the help of php, it is very easy to upload files to the server. PHP file upload features allows you to upload binary and text files both. Depending upon the requirement one can upload single and multiple files through PHP script by modifying the few line of codes.
PHP $_FILES

The PHP global $_FILES contains all the information of file. By the help of $_FILES global, we can get file name, file type, file size, temp file name and errors associated with file.

Lets see the more examples, through which you will learn how to access the $_FILES global.

$_FILES['filename']['name']

It will return the file name

$_FILES['filename']['type']

It will return MIME type of the file.

$_FILES['filename']['size']
It will return size of the file in bytes.

for more description : http://www.skptricks.com/2017/10/php-file-upload-using-post-method.html