undefinedp

       undefinedp()  -  determine whether or not a given variable
       is undefined.

SYNOPSIS

       int undefinedp( mixed arg );

DESCRIPTION

       Return 1 if `arg' is undefined.  'arg' will  be  undefined
       in the following cases:

       1.     it is a variable set equal to the return value of a
              call_other to a non-existent  method  (e.g.  arg  =
              call_other(obj, "???")).

       2.     it  is  a variable set equal to the return value of
              an access of an element in a mapping  that  doesn't
              exist (e.g. arg = map[not_there]).

SEE ALSO

       mapp(3),  stringp(3),  pointerp(3),  objectp(3),  intp(3),
       bufferp(3), floatp(3), functionp(3), nullp(3), errorp(3)