calculating values from input, in PHP

Question

I'm studying for finals and i came across this question:

Write a php script to read a positive integer, n from a input box and calculate the value of 1+2+-- n...

ive have tried for long and done sufficient research, but i have not been able to complete this so far i have:

<html>
  <head>
    <title>
     </title>
 </head>
 <body>
  <form action="inputnum.php" method="post" >
   num:<input type="text" name="num" size ="5"/>
  <input type = "submit" value = "Submit Order" />

       <?php
        $num=$_POST["num"];
        if ($num==0)$num=="";
         for($i=0; $i<=$num; $i++){
         }
            echo"($num+$i)";
       ?>

  </form>

can anyone help me out? Thanks in advance!

Fabrizio Calderan · Accepted Answer · 2012-04-18 10:40:07Z

4

<?php
  $num   = (int)$_POST["num"];
  $total = 0;

  for ($i=0; $i <= $num; $i++) {
     $total = $total + $i;
  }

  echo $total;
?>

If your code is expecting to deal with a number, it's better to do an explicit casting via (int) of the posted value

answered Apr 18, 2012 at 10:40

Fabrizio Calderan

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Comments

matino · Accepted Answer · 2012-04-18 10:43:31Z

2

You mixed up paranthesis, you also mix = with ==. Anyway there exists a faster way of computing such sum, i.e. n * (n + 1) / 2

answered Apr 18, 2012 at 10:43

matino

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1 Comment

mishu Over a year ago

sorry.. I removed my answer, I did not see that you pointed out this before.. +1 for showing the smart solution :)

heyanshukla · Accepted Answer · 2012-04-18 10:41:26Z

0

<?php
    $num=$_POST["num"];
    if ($num==0)$num="";
    else
    {
     for($i=0; $i<=$num; $i++){
       $sum=$sum+$i;
       }
    }
    echo $sum;
   ?>

To be more precise you must first check whether the submit button is set or not before calculating the sum.

answered Apr 18, 2012 at 10:41

heyanshukla

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Comments

Anriëtte Myburgh · Accepted Answer · 2012-04-18 10:43:39Z

0

Firstly, this if ($num==0)$num==""; is wrong. $num=""; is what it should be. And in anycase, this would break your if-statement.

I would suggest putting the for-loop in the if-statement and changing the condition to $num>0.

Let $i begin from 1, not 0.

answered Apr 18, 2012 at 10:43

Anriëtte Myburgh

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Comments

sorcix · Accepted Answer · 2012-04-18 10:43:53Z

0

You could use something like this (not tested, no PHP interpreter available here):

<html>
    <head>
        <title></title>
    </head>
    <body>

        <?php

            $num = (int)$_POST['num'];

            if(!$num) {

        ?>

        <form action="inputnum.php" method="post" >

            num: <input type="text" name="num" size ="5"/>
            <input type = "submit" value = "Submit Order" />

        </form>

        <?php

            } else {

                $total = 0;
                for($i=1; $i<=$num; $i++){

                    $total = $total + $i;

                }
                echo $num;

            }

        ?>

    </body>
</html>

answered Apr 18, 2012 at 10:43

sorcix

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