i use certain suffix in my variable name, a combination of an underscore and a property. such as :
$variable_html = variable that will be parse in html code.
$variable_str = string variable
$variable_int = integer variable
$variable_flo = float variable.
Do you have other visual clues? Maybe something you write for variable, function name, class strucure, or other stuff that helps others to read and not only for compiler ?