Php calculator using one input form

Question

4.00/5 (1 vote)

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Quote:
when i do any operation it work ok like 5+6 = 11, but again if i want to add say a number 5 to the evaluated answer its showing error that means only one time i can do operation again if i want to do operation its showing error. How to fix this issue any suggestion ?

What I have tried:

<?php
// current formula in input box
if (isset($_POST['txt'])) {
    $current_txt = $_POST['txt'];
}

if (isset($_POST['select1'])) {
  $message = "1";
}
if (isset($_POST['select2'])) {
  $message = "2";
}
if (isset($_POST['select3'])) {
  $message = "3";
}
if (isset($_POST['select4'])) {
  $message = "4";
}
if (isset($_POST['select5'])) {
  $message = "5";
}
if (isset($_POST['select6'])) {
  $message = "6";
}
if (isset($_POST['select7'])) {
  $message = "7";
}
if (isset($_POST['select8'])) {
  $message = "8";
}
if (isset($_POST['select9'])) {
  $message = "9";
}
if (isset($_POST['select0'])) {
  $message = "0";
}
if (isset($_POST['select+'])) {
  $message = "+";
}
if (isset($_POST['select-'])) {
  $message = "-";
}
if (isset($_POST['select/'])) {
  $message = "/";
}
if (isset($_POST['select*'])) {
  $message = "*";
}
if (isset($_POST['clear'])) {
  $message = "clear";
}
if (isset($_POST['calculate'])) {
  $message = "calc";
}

if ($message == "calc") {
    // Calculate using eval 
    $current_txt .= " = " . eval('return ' . $current_txt . ';');
} else {
    // Append input to formula
    $current_txt .= $message;
}

if ($message == "clear") {
    $current_txt = "";
}

?>

<div style="padding-left: 200px; margin-top: 100px">
  <form  method="post">
    Enter value:  <input type="text" name="txt" value="<?php
    echo $current_txt;
?>" >
    <div style="padding-left: 105px"><br>

      <input type="submit" name="select1" value="1">
      <input type="submit" name="select2" value="2">
      <input type="submit" name="select3" value="3">
      <input type="submit" name="select4" value="4"><br><br>
      <input type="submit" name="select5" value="5">
      <input type="submit" name="select6" value="6">
      <input type="submit" name="select7" value="7">
      <input type="submit" name="select8" value="8"><br><br>
      <input type="submit" name="select9" value="9">
      <input type="submit" name="select0" value="0">
      <input type="submit" name="select+" value="+">
      <input type="submit" name="select-" value="-"><br><br>
      <input type="submit" name="select/" value="/">
      <input type="submit" name="select*" value="*">
      <input type="submit" name="clear" value="clear"> <br><br>
      <input type="submit" name="calculate" value="calculate">

    </div>

  </form>
</div>

Posted 9-Apr-18 23:01pm

123456patil

Updated 10-Apr-18 6:34am

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Comments

Sunasara Imdadhusen 10-Apr-18 5:48am

You must convert your value into number

123456patil 10-Apr-18 7:12am

ok thank you

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W∴ Balboos, *GHB* · Answer 1 · 2018-04-10T06:36:00

Once you get your total, what do you do with the result?

You need to put the result in some storage and have your application look for it if it does not have enough input elements (i.e., you didn't start with a new a+b)

something like this (pseudocode) for addtion:

// Assuming 'a' is the first of the pair of operators
  if(b is undefined) b = c;
  c = a + b;
  write c;

Now the above doesn't work (as written) for the first input - it's only an example showing you that if you wish to add a second number to the result AFTER an operation you need to have some way to recall and use the old answer for the new operation.