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This calculator script can:
1. add
2. subtract
3. multiply
4. divide
5. square numbers
6. calculate square roots
7. calculate powers
Error checking
---------------
If any of the two input fields are left empty, PHP will add in a random value between 1 and 100. If the rounding field is left empty, PHP will set the amount of precision for the rounding to 0 digits.
It is mathematically impossible to raise a negative number to a decimal. Therefore PHP will display an error with a link explaining this error to the user.
Code
---------
Appropriate numbers are rounded according to the users input. This means numbers from division, and square roots will be rounded. Uses radio buttons for the operator, and a switch case statement. Therefore I believe it is easily expandable.
<?php
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Calculator</title>
</head>
<body>
<?php
// basic calculator program
function showForm() {
?>
All field are required, however, if you forget any, we will put a random number in for you. <br />
<table border="0">
<form action="<?php echo $_SERVER['PHP_SELF'];?>" method="post">
<tr>
<td>Number:</td>
<td><input type="text" maxlength="3" name="number" size="4" /></td>
</tr>
<span id="square">
<tr>
<td>Another number:</td>
<td><input type="text" maxlength="4" name="number2" size="4" /></td>
</tr>
</span>
<tr>
<td valign="top">Operator:</td>
<td><input type="radio" name="opt" value="+" </>+<br />
<input type="radio" name="opt" value="-" />-<br />
<input type="radio" name="opt" value="*" />*<br />
<input type="radio" name="opt" value="/" />/<br />
<input type="radio" name="opt" value="^2" />x<sup>2</sup><br />
<input type="radio" name="opt" value="sqrt" />sqrt<br />
<input type="radio" name="opt" value="^" />^<br />
</td>
</tr>
<tr>
<td>Rounding:</td>
<td><input type="text" name="rounding" value="4" size="4" maxlength="4" /></td>
<td><small>(Enter how many digits you would like to round to)</small>
</td>
</tr>
<tr>
<td><input type="submit" value="Calculate" name="submit" /></td>
</tr>
</form>
</table>
<?php
}
if (empty($_POST['submit'])) {
showForm();
} else {
$errors = array();
$error = false;
if (!is_numeric($_POST['number'])) {
(int)$_POST['number'] = rand(1,200);
}
if (empty($_POST['number'])) {
(int)$_POST['number'] = rand(1,200);
}
if (!is_numeric($_POST['number2'])) {
(int)$_POST['number2'] = rand(1,200);
}
if (empty($_POST['number2'])) {
(int)$_POST['number2'] = rand(1,200);
}
if (empty($_POST['rounding'])) {
$round = 0;
}
if (!isset($_POST['opt'])) {
$errors[] = "You must select an operation.";
$error = true;
}
if (strpbrk($_POST['number'],"-") and strpbrk($_POST['number2'],"0.") and $_POST['opt'] == "^") {
$errors[] = "You cannot raise a negative number to a decimal, this is impossible. <a href=\"http://hudzilla.org/phpwiki/index.php?title=Other_mathematical_conversion_functions\">Why?</a>";
$error = true;
}
if ($error != false) {
echo "We found these errors:";
echo "<ul>";
foreach ($errors as $e) {
echo "<li>$e</li>";
}
echo "</ul>";
} else {
switch ($_POST['opt']) {
case "+":
$result = (int)strip_tags($_POST['number']) + (int)strip_tags($_POST['number2']);
echo "The answer to " . (int)strip_tags($_POST['number']) . " $_POST[opt] " . (int)strip_tags($_POST['number2']) . " is $result.";
break;
case "-";
$result = (int)strip_tags($_POST['number']) - (int)strip_tags($_POST['number2']);
echo "The answer to " . (int)strip_tags($_POST['number']) . " $_POST[opt] " . (int)strip_tags($_POST['number2']) . " is $result.";
break;
case "*";
$result = (int)strip_tags($_POST['number']) * (int)strip_tags($_POST['number2']);
echo "The answer to " . (int)strip_tags($_POST['number']) . " $_POST[opt] " . (int)$_POST['number2'] . " is $result.";
break;
case "/";
$result = (int)strip_tags($_POST['number']) / (int)strip_tags($_POST['number2']);
$a = ceil($result);
echo "<br />";
echo "<hr />";
echo "<h2>Rounding</h2>";
echo "$result rounded up is $a";
echo "<br />";
$b = floor($result);
echo "$result rounded down is $b";
echo "<br />";
$h = round($result,(int)$_POST['rounding']);
echo "$result rounded to $_POST[rounding] digits is " . $h;
break;
case "^2":
$result = (int)strip_tags($_POST['number']) * (int)strip_tags($_POST['number2']);
$a = (int)$_POST['number2'] * (int)$_POST['number2'];
echo "The answer to " . (int)$_POST['number'] . "<sup>2</sup> is " . $result;
echo "<br />";
echo "The answer to " . (int)$_POST['number2'] . "<sup>2</sup> is " . $a;
break;
case "sqrt":
$result = (int)strip_tags(sqrt($_POST['number']));
$sqrt2 = (int)strip_tags(sqrt($_POST['number2']));
echo "The square root of " . (int)strip_tags($_POST['number']) . " is " . $result;
echo "<br />";
echo "The square root of " . (int)strip_tags($_POST['number2']) . " is " . $sqrt2;
echo "<br />";
echo "The square root of " . (int)strip_tags($_POST['number']) . " rounded to " . strip_tags($_POST[rounding]) . " digits is " . round($result,(int)$_POST['rounding']);
echo "<br />";
echo "The square root of " . (int)strip_tags($_POST['number2']) . " rounded to " . strip_tags($_POST[rounding]) . " digits is " . round($sqrt2,(int)strip_tags($_POST['rounding']));
break;
case "^":
$result = (int)strip_tags(pow($_POST['number'],$_POST['number2']));
$pow2 = (int)strip_tags(pow($_POST['number2'],$_POST['number']));
echo (int)$_POST['number'] . "<sup>" . strip_tags($_POST[number2]) . "</sup> is " . $result;
echo "<br />";
echo (int)$_POST['number2'] . "<sup>" . strip_tags($_POST[number]) . "</sup> is " . $pow2;
break;
}
}
}
echo "<br />";
?>
<a href="calc.php">Go Back</a>
</body>
</html>
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