DAte use in For loop

Hi All

please give one  help

I want to us date variable in for loop Condition. in PHP

But it not working Properly.
$dt='2003-04-22' ;
$to='2003-04-30';

FOR ( $dt=$dt; $dt > $to ;  )
{
print "XYz";
}

Please Help me

and how to file date diff in Day please Help

Ramesh Patel