PHP mortgage calculation

  function debx()
  {
    $dkm   = 360; //贷款月数，20年就是240个月
    $dkTotal = 390000; //贷款总额
    $dknl  = 0.049; //贷款年利率
    $emTotal = $dkTotal * $dknl / 12 * pow(1 + $dknl / 12, $dkm) / (pow(1 + $dknl / 12, $dkm) - 1); //每月还款金额
    $lxTotal = 0; //总利息
    for ($i = 0; $i < $dkm; $i++) {
      $lx   = $dkTotal * $dknl / 12;  //每月还款利息
      $em   = $emTotal - $lx; //每月还款本金
      echo "第" . ($i + 1) . "期", " 本金:", $em, " 利息:" . $lx, " 总额:" . $emTotal, "<br />";
      $dkTotal = $dkTotal - $em;
      $lxTotal = $lxTotal + $lx;
    }
    echo "总利息:" . $lxTotal;
  }
    
    
  function debj()
  {
    $dkm   = 360; //贷款月数，20年就是240个月
    $dkTotal = 390000; //贷款总额
    $dknl  = 0.049; //贷款年利率
       
    $em   = $dkTotal / $dkm; //每个月还款本金
    $lxTotal = 0; //总利息
    for ($i = 0; $i < $dkm; $i++) {
      $lx   = $dkTotal * $dknl / 12; //每月还款利息
      echo "第" . ($i + 1) . "期", " 本金:", $em, " 利息:" . $lx, " 总额:" . ($em + $lx), "<br />";
      $dkTotal -= $em;
      $lxTotal = $lxTotal + $lx;
    }
    echo "总利息:" . $lxTotal;
  }
    
   debx(); 
  exit;