excel PMT formula to PHP help ?

[sasori]

hi, how to convert this excel spreadsheet into PHP ?

 

 

B3 = principal = 1,934
B4 = interest flat rate = 15% fixed
B5 = tenor in months = 60 fixed
 
B10 = monthly = $46.01
 

 

the formula for cell B10 is 

 

 PMT(B4/12,B5,B3)

 

so how did the B10 became 46.01

[kicken]

Some google searching lead to http://www.tvmcalcs.com/tvm/formulas/regular_annuity_formulas that describes the actual math formulas behind the function. The one you're interested in is probably the third one: Periodic Payment when PV is known

[AndyGee]

Something like this?

function pmt($apr, $loanlength, $loanamount){
    $apr /= 1200;
    return ($apr * -$loanamount * pow((1 + $apr), $loanlength) / (1 - pow((1 + $apr), $loanlength)));
}

for 18%APR over 8 months on a principal of 1099
 

pmt(18, 8, 1099);

=146.80884303075