Urgent !!! my .php file can't work in another PHP version

hi Sir/Madam, recently i put one of my .php file to my friend's server (using PHP v4.2.3) from my server (using PHP v.4.0.6) However, when i browse my file in the browser, it shows out : Notice: Undefined variable: op in F:\avteam\stbc_hp\noticeboard.php on line 674 Notice: Undefined offset: 1 in F:\avteam\stbc_hp\noticeboard.php on line 42 Notice: Undefined variable: PHP_SELF in F:\avteam\stbc_hp\noticeboard\theme.php on line 2 this thing doesn't happen in my server b4 and it 100% no bug to run in my server. is it that i need to declare the variable b4 use? OR, if i DON' T want to declare the variable is there any alternative method to avoid the aboved problem? pls let me know if u need my source codes. many thx as i'm in urgent, regards, Joshua