how to use Recurring Deposits formula in php -

i not know how use recurring deposits formula in php calculate rd.please give me code calculate recurring deposits.

$m; $r=200; $n=4; $i=11;  m =r [ (1+i)n – 1]      --------------------          1- (1+i) -1/3   m = maturity value r = monthly installment n = number of quarters = rate of interest/400   echo $m; ?> 

$m = ($r * ((($i+1)*$n)-1))/(1-($i+1)-(1/3)); 

but eliyahu said - need learn basics of variables , operations first ;)

full code like:

$r=200; $n=4; $i=11;  $m = ($r * ((($i+1)*$n)-1))/(1-($i+1)-(1/3)); echo $m;