Can't work out how to loop and increase my values

Question

I am trying to create a function that will return an array of future payment and dates.

function getFuturePayments(){
    $intMap = array();

    $startVal     = 1000.00;
    $startDate    = '2013-04-02';
    $interest     = 2.843; //(39.9% apr)
    $minPayment   = 62.92;
    $intMap['00 - ' . date('o-m-d', strtotime($startDate))] = $startVal;

    //----------------------------------------------
    $int = $startVal * ($interest / 100);
    $lastPayemt  = $startVal + $interestAmount - $minPayment;

    $intMap[sprintf('%02s', 1) .' - 2013-04-30'] = sprintf('%0.2f', $lastPayemt);

 return $intMap;

}

This all works as expected and intended but when I add a for loop to increase the date by 28 days, and do the math for the amount remaining. I am lost as to what I am doing wrong.

This is what I am hoping to happen.

//----------------------------------------------
$int2 = $lastPayemt * ($interest / 100);
$interestAmount2 = $this->roundUp($int2, 2);
$nextPayment = $lastPayemt + $interestAmount2 - $minPayment;

$intMap['02 - 2013-05-28'] = $nextPayment;
//----------------------------------------------
$int2 = $nextPayment * ($interest / 100);
$interestAmount2 = $this->roundUp($int2, 2);
$nextPayment = $nextPayment + $interestAmount2 - $minPayment;

$intMap['03 - 2013-06-25'] = $nextPayment;
//----------------------------------------------
$int2 = $nextPayment * ($interest / 100);
$interestAmount2 = $this->roundUp($int2, 2);
$nextPayment = $nextPayment + $interestAmount2 - $minPayment;

$intMap['04 - 2013-07-23'] = $nextPayment;
//----------------------------------------------

But cant work out how to do it in a for loop.

for($i=0; $i < 27; $i++){ //hard coded for now      
    $date = date('o-m-d', strtotime($startDate .' + 28 days'));
    $int2 = $lastPayemt * ($interest / 100);
    $interestAmount2 = $this->roundUp($int2, 2);
    $nextPayment = $lastPayemt + $interestAmount2 - $minPayment;

   $intMap[ $i .' - ' . date('o-m-d', strtotime($date)) ] = $nextPayment;
}

Outputs

[0 - 2013-04-30] => 1114.8

[1 - 2013-04-30] => 1114.8

[2 - 2013-04-30] => 1114.8

[3 - 2013-04-30] => 1114.8

[4 - 2013-04-30] => 1114.8

[5 - 2013-04-30] => 1114.8

[6 - 2013-04-30] => 1114.8

[7 - 2013-04-30] => 1114.8

[8 - 2013-04-30] => 1114.8

[9 - 2013-04-30] => 1114.8

[10 - 2013-04-30] => 1114.8

[11 - 2013-04-30] => 1114.8

...

But this just adds the same value over and over.

Thanks to BlackMambo i have got to this -

for($i=0; $i < 27; $i++){ //hard coded for now    
    $date = date('o-m-d', strtotime($startDate . ' + 28 days'));
    $int = $lastPayemt * ($interest / 100);
    $interestAmount = $this->roundUp($int, 2);  

    $nextPayment = $lastPayemt + $interestAmount - $minPayment;
    $lastPayemt = $nextPayment + $interestAmount - $minPayment;         

    $intMap[ $i .' - ' . date('o-m-d', strtotime($date)) ] = $nextPayment;
}

Still having trouble increment the date tho.
Finally got it all working thanks Guys.

for($i=1; $i < 27; $i++){ //hard coded for now 

    $lastDate = date('o-m-d', strtotime($startDate));
    $lastDate = date('o-m-d', strtotime($lastDate . ' + 28 days'));
    $startDate = date('o-m-d', strtotime($lastDate));

    $int = $lastPayemt * ($interest / 100);
    $interestAmount = $this->roundUp($int, 2);  

    $nextPayment = $lastPayemt + $interestAmount - $minPayment;
    $nextPayment = $nextPayment + $interestAmount - $minPayment;
    $lastPayemt = $nextPayment;                 


    $intMap[sprintf('%02s', $i).' - '.date('o-m-d',strtotime($lastDate))]=$nextPayment;


}

The Final working function

function getFuturePayments($startAmount, $startFromDate, $baseInterest, $minPayment){
    $intMap = array();

    $startVal     = $startAmount;
    $startDate    = $startFromDate;
    $interest     = $baseInterest; //(39.9% apr / 34.1% compouned)
    $minPayment   = $minPayment;

    $intMap['00 - ' . date('o-m-d', strtotime($startDate))] = $startVal;
    //-----------------------------------------------------------------
    $int = $startVal * ($interest / 100);
    $interestAmount = roundUp($int, 2);
    $lastPayemt = $startVal + $interestAmount - $minPayment;

    $startDate = date('o-m-d', strtotime($startDate . ' + 28 days'));

    for($i=1; $lastPayemt > 0; $i++){       
        $int = $lastPayemt * ($interest / 100);
        $interestAmount = roundUp($int, 2);
        $nextPayment = $lastPayemt;

        $lastDate = date('o-m-d', strtotime($startDate));
        $lastDate = date('o-m-d', strtotime($lastDate));
        $startDate = date('o-m-d', strtotime($lastDate . ' + 28 days'));

        $intMap[ sprintf('%02s', $i) . ' - ' . date('o-m-d', strtotime($lastDate)) ] =  sprintf('%0.2f', $nextPayment);

        $lastPayemt = $nextPayment + $interestAmount - $minPayment;         
        }
    return $intMap;
    }
//roundUp function from an answer here http://stackoverflow.com/questions/8239600/rounding-up-to-the-second-decimal-place
function roundUp ($value, $precision){ 
    $pow = pow(10, $precision); 
    return (ceil($pow * $value) + ceil($pow * $value - ceil($pow * $value))) / $pow; 
}

edit(added syntax correction + output).
edit2(Updated with new for loop).
edit3(Finally working added working code).
edit4(Added fully functional function).

The date on the first line of your for loop always equals `$startDate + 28 days` — andrewsi, May 06 '13 at 17:34
Are you supposed to be incrementing `$i` days instead of `+ 28 days` in the loop? — jeffjenx, May 06 '13 at 17:34

blackmambo · Accepted Answer · 2013-05-06T17:56:08.203

1

Several values in your loop havent changed. Such as startdate, interest and the date. If these values arent reassigned a new value, you will continue to get the same output.

//example ONLY,
$startDate = $lastDate;
$lastpayment = xyz;

You can even use var_dump($startdate, $lastpayment, $interest) to see what I am talking about.

edited May 06 '13 at 17:56

answered May 06 '13 at 17:37

blackmambo

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Vote for my answer if is helped u. Glad I could help, thanks! :) – blackmambo May 06 '13 at 17:57

Can't work out how to loop and increase my values

1 Answers1