nil and default

[Cogs]

I wouldn't know where to look for documentation at php.net for these... constants, keywords or other.

What does nil and default do?

[planetsim]

do you mean null

null basically means nothing or in plan english the there is no value so e.g.

$value = null;

$value has no value.

TO find out about constants etc.

http://www.php.net/manual/en/language.constants.php

[Cogs]

so what is the difference between nill and null?

I checked that page, it didn't have anything on nill or default.

[tomkleijkers]

Where are you trying to use these variables?

Null = nil and means 'no value', it's a discussion because some people say that a good programmer never uses null values, but other people tell it doesn't matter to use them.

Default has no meaning, only when used somewhere. i.e. If you use:

switch($value){
   case a:
       $value = 'a';
       break;

   default:
      $value = 'no value';
      break;
}

than default has a meaning: the default action. So please tell why and where you want to use them.