Question

我是PHP的新手，现在检查该功能是如何工作的。我在futurevalue.php中有3个函数，正在从display_results.php中调用。

我想使用我的函数获得结果： 1. future_value将返回未来值的计算值 2. currency_formatting将使用$ sign返回2个值：$ investment_f，$ future_value_f 3. percent_formatting将使用百分号

返回值$ annual_rate_f

目前，没有值返回到display_results.php，我也想知道我的函数调用是否正确。

感谢您的回应。

futurevalue.php

<?php

namespace murach\futurevalue{

    // Calculate the future value
    if(!function_exists('future_value')){
        function future_value($investment,$years, $yearly_rate) {
            global $future_value;
            $future_value = $investment;;


            if (isset($_POST['compound_monthly'])) {
                // compound monthly
                $compounded_monthly = 'Yes';
                $months = $years * 12;
                $monthly_rate = $yearly_rate / 12;
                for ($i = 1; $i <= $months; $i++) {
                    $future_value = $future_value + ($future_value * $monthly_rate *.01);
                }
            } else {
                // compound yearly
                $compounded_monthly = 'No';
                for ($i = 1; $i <= $years; $i++) {
                    $future_value = $future_value + ($future_value * $yearly_rate *.01);
                }
            }  

            return $future_value;
        }
    }
    //Function for currency formatting
    if(!function_exists('currency_formatting')){
        function currency_formatting($investment, $future_value) {
            if(isset( $investment_f)){
                $investment_f = '$'.number_format($investment, 2);
                //   return $investment_f;


                $future_value_f = '$'.number_format($future_value, 2);
                return array($investment_f, $future_value_f);
            }
        }
    }

    //Function for percent formatting
    if(!function_exists('percent_formatting')){
        function percent_formatting( $yearly_rate) {
            if(isset( $yearly_rate_f)){

                $yearly_rate_f = $yearly_rate.'%';
                return $yearly_rate_f;
            }
        }
    }
}
?>

display_results.php

<?php
require('C:\xampp\htdocs\ex_solutions\ch07_en7-1\futurevalue.php');

// get the data from the form
if(isset($_POST['investment'])) {
    $investment = $_POST['investment'];
}

if(isset($_POST['interest_rate'])) {
    $yearly_rate = $_POST['interest_rate'];
}

if(isset($_POST['years'])) {
    $years = $_POST['years'];
}
if (isset($_POST['compounded_monthly'])){
    $compounded_monthly = $_POST['compound_monthly'];
}


// validate investment entry
if ( empty($investment) ) {
    $error_message = 'Investment is a required field.'; 
} else if ( !is_numeric($investment) )  {
    $error_message = 'Investment must be a valid number.'; 
} else if ( $investment <= 0 ) {
    $error_message = 'Investment must be greater than zero.';        
    // validate interest rate entry
} else if ( empty($yearly_rate) ) {
    $error_message = 'Interest rate is a required field.'; 
} else if ( !is_numeric($yearly_rate) )  {
    $error_message = 'Interest rate must be a valid number.'; 
} else if ( $yearly_rate <= 0 ) {
    $error_message = 'Interest rate must be greater than zero.';        
    // set error message to empty string if no invalid entries
} else {
    $error_message = '';
}

// if an error message exists, go to the index page
if ($error_message != '') {
    include('index.php');
    exit();
}

require_once('C:/xampp/htdocs/ex_solutions/ch07_en7-1/futurevalue.php');
$future_value = murach\futurevalue\future_value($investment, $yearly_rate, $years);


require_once('C:\xampp\htdocs\ex_solutions\ch07_en7-1\futurevalue.php');
$investment_f = murach\futurevalue\currency_formatting($investment, $future_value);

require_once('C:\xampp\htdocs\ex_solutions\ch07_en7-1\futurevalue.php');
$future_value_f = murach\futurevalue\currency_formatting($investment, $future_value);

require_once('C:\xampp\htdocs\ex_solutions\ch07_en7-1\futurevalue.php');
$yearly_rate_f =  murach\futurevalue\percent_formatting( $yearly_rate);

?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Future Value Calculator</title>
<link rel="stylesheet" type="text/css" href="main.css"/>
</head>
<body>
<div id="content">
    <h1>Future Value Calculator</h1>

    <label>Investment Amount:</label>
    <span><?php echo $investment_f; ?></span><br />

    <label>Yearly Interest Rate:</label>
    <span><?php echo $yearly_rate_f; ?></span><br />


    <label>Number of Years:</label>
    <span><?php echo $years; ?></span><br />

    <label>Future Value:</label>
    <span><?php echo $future_value_f; ?></span><br />


    <label>Compound Monthly:</label>
   <span><?php  murach\futurevalue\future_value($compounded_monthly);  ?></span><br />


</div>
</body>
</html>

Answer 1

您有多个逻辑问题

a）require_once()重复多次，但始终需要相同的文件。这毫无意义。 require_once()和include_once()将加载指定的ONCE然后再次尝试加载相同的文件变为空操作。

b）你有这个：

function currency_formatting($investment, $future_value) {
    if(isset( $investment_f)){
               ^^^^^^^^^^^^---- undefined variable

由于$investment_f未定义，因此您永远无法拨打number_format()或return来电，因此您的功能只会从底部掉落并且不会返回任何内容。不返回任何内容的函数将是隐式null值：

function foo() {
  // do nothing
}

$bar = foo(); // $bar becomes null

c）您正在对数值使用empty()测试。 empty(0)恰好是正确的，所以如果计算一笔0％APR汽车贷款的贷款，你就会失去无效的代码路径。

PHP函数没有返回任何值

1 个答案: