I am not sure if I understand what you mean by 'negative result' (e.g. you might mean 'findings were the opposite of those expected' or 'findings were null'). Also, by 'deter the confering' I presume you mean 'fail'. But if your question is 'If I don't get the results I expected, will I fail my PhD', then answer is no, because the way the research was conducted and interpreted etc is generally of much more importance than the findings. Sorry if I am misunderstanding your question though.