Manual:Hooks/UploadVerifyFile

Details

 * : an instance of, with all info about the upload.
 * : the uploaded file's mime type, as detected by MediaWiki. Handlers will typically only apply for specific mime types.
 * : output true if the file is valid. Otherwise, an indexed array representing the problem with the file, where the first element is the message key and the remaining elements are used as parameters to the message.