Question

我在使用输入代码处理等式时遇到了一些问题。我已经尝试了一段时间（我是新编码）和搜索，但却无法以任何方式使其工作。这就是我最终的结果。谁能帮我？提前谢谢。

<!DOCTYPE HTML>
<html> 
<body>

<form action="" method="post">
<br />Choose a number to be the nth in the Fibonacci sequence: <input type="number" name="fibnum">
<input type="submit">
</form> <br /> <br />

<?php


if(isset($_POST['fibnum'])){


    $fibnum = $_POST['fibnum'];


    function fibRec($fibnum){

        if ($fibnum < 0){
        echo "There are no Fibonacci numbers of negative values.";
        }
            elseif ($fibnum == 0){

                echo "0";
            }

                elseif ($fibnum == 1){

                    echo "1";
                }

                    else {

                        $sum = fibRec($fibnum-1)+fibRec($fibnum-2); 
                        echo $sum;
                    }

    }
        $fib = fibRec($fibnum); 
        echo $fib;          

}           
?>    

</body>
</html>

Answer 1

使其工作只需要将回声改为如下所示的回报：

<?php
$_POST['fibnum']=11;

if(isset($_POST['fibnum'])){


    $fibnum = $_POST['fibnum'];


    function fibRec($fibnum){

        if ($fibnum < 0){
        return ( "There are no Fibonacci numbers of negative values.");
        }
            elseif ($fibnum == 0){

                return ("0");
            }

                elseif ($fibnum == 1){

                    return ("1");
                }

                    else {

                        $sum = fibRec($fibnum-1)+fibRec($fibnum-2); 
                        return ($sum);
                    }

    }
        $fib = fibRec($fibnum); 
        echo $fib;          

}           
?>

工作演示：https://issues.apache.org/jira/browse/SPARK-4705

Answer 2

你正在把整数推向回声。在递归公式中，返回值将返回到调用实体，而不是在函数外部自动返回。

看看这个：

<!DOCTYPE HTML>
<html> 
<body>

<form action="" method="post">
<br />Choose a number to be the nth in the Fibonacci sequence: <input type="number" name="fibnum">
<input type="submit">
</form> <br /> <br />

<?php


if(isset($_POST['fibnum'])){


    $fibnum = $_POST['fibnum'];


    function fibRec($fibnum){

        if ($fibnum < 0){
        echo "There are no Fibonacci numbers of negative values.";
        }
            elseif ($fibnum == 0){

                return 0;
            }

                elseif ($fibnum == 1){

                    return 1;
                }

                    else {

                        $sum = fibRec($fibnum-1)+fibRec($fibnum-2); 
                        return $sum;
                    }

    }
        $fib = fibRec($fibnum); 
        echo $fib;          

}           
?>    

</body>
</html>

Answer 3

您还可以使用与黄金比率相关的PHI常数来计算第n个斐波那契数。认为直到第5次迭代的斐波那契数都不是黄金比率，所以您可以像下面这样：

<?php 

$fibnum = intval($_POST['fibnum']);

const PHI = 1.6180339887;
$f = [0, 1, 1, 2, 3];

echo getNthFibo($fibnum);

function getNthFibo($i)
{
    if($i < 5){
        return $f[$i];
    }

    // Starting from 5th iteration of fibo function
    $n = 5;
    $fn = 3;

    while ($n < $i) { 
        $fn = round($fn * PHI); 
        $n++; 
    }

    return $fn; 
}

通过输入字段PHP查找第N个Fibonacci数

3 个答案: