can't write into files using system() in PHP

HI,
I am able to call system("date") and it works properly but when i give system("date >temp") it gives me an error.when i try to execute processes where i write into files i am not able to do it
please help!!!!!
say I give a
if(system("date")==false){echo"<p>error";}
..it gives me the correct date and time in LINUX.
but when i give

if(system("date >temp")==false) {echo"<p>error";}
..it prints error

same if i give say a ./a.out
if ./a.out doesnt write into any file it works fine...

but if the process writes into any file it gives an error.
it is unable to.

SHOULD I CHANGE SOMETHING IN MY httpd.conf or php.ini??

THIS IS ON LINUX

from sumanth

Would you please elaborate your question a little more.