Different laravel validation rules

gistfile1.txt

// mimetype mp4, max is in kilobytes
mimetypes:video/mp4|max:15000

// only images and max size of 500 KB
image|max:500

// exists checks the attribute value in a table exists, format is: {table},{column}
required|exists:projects,id

// mimetypes for documents like word, powerpoint, excel and pdf with max filesize of 5000 KB
mimes:doc,docx,ppt,pptx,xls,xlsx,pdf|max:5000

// image mimetypes allowed, max image dimensions specified in px
// Available constraints are: min_width, max_width, min_height, max_height, width, height, ratio.
image|nullable|dimensions:max_width=170,max_height=100