This is form for calculator
<form method='post' action='result.php' name='calc_form'>
<input type='text' name='input1' size='15'>
<select name='operation'>
<option value="plus">+</option>
<option value="minus">-</option>
<option value="multi">*</option>
<option value="invalid">**</option>
<option value="divide">/</option>
</select>
<input type='text' name='input2' size='15'>
<input type='submit' value='go'>
</form>
This is php with if elseif statement
<?php
define ('INVALID_INPUT', 'ERROR: invalid input');
define ('INVALID_OPERATOR', 'ERROR: invalid operator');
$result = null;
if
(isset($_POST) and
isset($_POST['input1']) and
isset($_POST['input2']) and
isset($_POST['operation']))
{
$input1 = $_POST['input1'];
$input2 = $_POST['input2'];
$operation = $_POST['operation'];
switch ($operation)
{
case 'plus':
$result = $input1 + $input2;
break;
case 'minus':
$result = $input1 - $input2;
break;
case 'multi':
$result = $input1 * $input2;
break;
case 'divide':
$result = $input1 / $input2;
break;
default:
$result = INVALID_OPERATOR;
break;
}
}
elseif
(!isset($_POST) and
isset($_POST['input1']) and
isset($_POST['input2']) and
isset($_POST['operation']))
{
$result = INVALID_INPUT;
}
if ($result !== null)
{
echo <<<EOM
<h2>you calculate</h2> $input1
<h2>and</h2> $input2
<h2>result is:</h2>
$result
EOM;
}
?>
I even tried with only else statement and without condition but it wont show INVALID INPUT when nothing is added in form. What is wrong here?
The problem is with this piece of code:
if
(isset($_POST) and
isset($_POST['input1']) and
isset($_POST['input2']) and
isset($_POST['operation']))
Even if a user enters nothing in the input fields, they will still pass isset($_POST['input1']), since they are 'set' to an empty string. Try switching it to this instead:
if
(isset($_POST['input1']) && strlen($_POST['input1']) &&
isset($_POST['input2']) && strlen($_POST['input2']) &&
isset($_POST['operation']))
Your condition is wrong; this is impossible:
!isset($_POST) and
isset($_POST['input1']) and
isset($_POST['input2']) and
isset($_POST['operation'])
I suspect you mean
!isset($_POST) or
!isset($_POST['input1']) or
!isset($_POST['input2']) or
!isset($_POST['operation'])
You could just use an else statement instead of an else if statement. That way if you change the inputs you don't have to list each of them twice.
eg:
if (isset($_POST) and
isset($_POST['input1']) and
isset($_POST['input2']) and
isset($_POST['operation']))
{
// result = calculation
} else
{
// result == code
}
Try this - I tested this on my server and it works!
calculator.php
<?php
error_reporting(E_ALL | E_STRICT);
ini_set('display_errors',1);;
define ('INVALID_INPUT', 'ERROR: invalid input');
define ('INVALID_OPERATOR', 'ERROR: invalid operator');
$input1 = $input2 = $operation = null;
if (isset($_POST['input1']) and isset($_POST['input2']) and isset($_POST['operation']))
{
$input1 = $_POST['input1'];
$input2 = $_POST['input2'];
$operation = $_POST['operation'];
if(is_numeric($input1) and is_numeric($input2))
{
switch ($operation)
{
case 'plus':
$result = $input1 + $input2;
break;
case 'minus':
$result = $input1 - $input2;
break;
case 'multi':
$result = $input1 * $input2;
break;
case 'divide':
$result = $input1 / $input2;
break;
default:
$result = INVALID_OPERATOR;
break;
}
}
else
{
$input1 = '';
$input2 = '';
$operation = 'invalid';
$result = INVALID_INPUT;
}
}
?>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
<title></title>
<meta name="description" content="">
<meta name="viewport" content="width=device-width, initial-scale=1">
</head>
<body class="">
<form method='POST' action='calculator.php'>
<input type='text' name='input1' size='15' value="<?php echo $input1; ?>">
<select name='operation'>
<option <?php if($operation == 'plus') { echo 'selected';} ?> value="plus">+</option>
<option <?php if($operation == 'minus') { echo 'selected';} ?> value="minus">-</option>
<option <?php if($operation == 'multi') { echo 'selected';} ?> value="multi">*</option>
<option <?php if($operation == 'invalid') { echo 'selected';} ?> value="invalid">**</option>
<option <?php if($operation == 'divide') { echo 'selected';} ?> value="divide">/</option>
</select>
<input type='text' name='input2' size='15' value="<?php echo $input2; ?>">
<span>=</span>
<input type='text' name='result' size='50' value="<?php echo $result; ?>">
<input type='submit' value='go'>
</body>
</html>