Uploading images

The submit-button has to have the attribute "name" with the value "submit", while the PHP script expects this name in the function 'isset'.
SD4 does not provide us with an Button with the attribute "name". 
Therefore this attribute and value are added to the button via Javascript.
Please, see the attached file "rjsmodifier.js".

Further instructions:
https://www.w3schools.com/php/php_file_upload.asp