Resources on handling file uploads.
http://php.net/manual/en/features.file-upload.php
http://php.net/manual/en/reserved.variables.post.php#87512
https://www.sitepoint.com/file-uploads-with-php/
https://www.sitepoint.com/monitoring-file-integrity/
Front end
https://www.quirksmode.org/dom/inputfile.html
https://www.sitepoint.com/tracking-upload-progress-with-php-and-javascript/
Related
https://www.sitepoint.com/monitoring-file-integrity/
https://www.sitepoint.com/html5-native-drag-and-drop-api/
Sulphur
https://github.com/KorvinM/sulphur