TIMESTAMP values are converted to the "zero"

[E.L.]

Hi 

I am runing MySql 3.22.25 and PHP3
and when i send  NOW(); as value 
the TIMESTAMP values are converted to the "zero"   00000000000000

and when i send  NOW('1997-10-04 22:23:00'); as value the
database return correctly 19971004222300

I try to have the current_date and it doesn't seem  to work

same thing for CURTIME();  CURDATE();  UNIX_TIMESTAMP();


Am i missing something

Etienne