Controlling HTML Form with PHP

rslucchese

Hello,

I am very new to PHP and am currently trying to emulate the windows calculator. I am trying to understand the notion of how to get a form button to communicate with PHP. For example, if a user presses the "5" button, I would like 5 to be appended onto the text field/display (if it is not the first digit, at which case the initial 0 that sits on the screen needs to be clared first). Here is what I have so far, the interface is built, and I have been trying to use the $_POST array then echo, but I cannot get the display value to change.

Thanks in advance,

Rafael.

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<?php
$inputText = 0;
$isFirstInput = true; // Determines if the number being pressed is the first
//in the display ("0." has to be replaced with the number plus ".")
$isFirstOperand = true; // Determines if the operand being stored is the one
//to the left side of the operator
$operator = ""; // Will store the name of the operator upon onRelease of a #btn
$reg1 = 0; // Stores a value in the memory. It will be a number
$operand1 = 0; //Stores first value in an operation statement
$operand2 = 0; //Stores the second value in the operation

//$formatted = number_format($number, 2);

//During the second operation, the program needs to be aware that a first
//operand and an operator already exist
function secondOperand($isFirstOperand)
{
$isFirstOperand = false; // Defines that the number is the second operand
return $isFirstOperand;
}

function doOperation($operand1, $operand2, $operator)
{
if(is_numeric($inputText)) / /
{
if($operator != null) / Operator info stored here /
{
switch($operator)
{
case "btnAdd" : $result= $operand1 + $operand2; break;
case "btnSub" : $result= $operand1 - $operand2; break;
case "btnMult" : $result= $operand1 * $operand2; break;
case "btnDiv" : $result= $operand1 / $operand2; break;
}

echo("Calculation result: $result");
//For testing only, this needs to output to the text box
}
}
else
{
echo("Invalid entry - please retry with numbers only.");
}
}

<html>
<head>
<title>Calculator</title>
<style>
/ All style information is embeded in this file in order to produce /
/ a single stand-alone file at the end of this project. /

.buttonSmall
{
width:45px; height:35px; margin:4px 0px 0px 0px;
}

.buttonLarge
{
width:78px; height:35px;
}

.display
{
margin-bottom:10px; width:284px; text-align:right;
}

#container
{
position:absolute; height:240px; width:300px;
background-color:#ccc; padding:20px 0px 0px 10px;
}

#topLeftSquare
{
position:relative; float:left; height:28px; width:30px;
background-color:#ccc; margin:3px 9px 0px 9px;
}
</style>
</head>

<body>

<div id="container">
<form action="$_SERVER['PHP_SELF']" method="post">
<input type="text" name="inputText" value="<?php echo $inputText; ?>" maxlength="35" class="display"><br/>
<div id="topLeftSquare"></div>

</body>

</html>

Horizon88

First off, please use the board's php code tags to make debugging/reading your code easier.

Secondly, if you're looking to append it to the text field immediately without a page refresh/processing call, you'd be better off using Javascript or another client-side language.

And thirdly, the reason I can see for your code not working is all you have are button inputs, but no submit buttons - your form can have as many clickable buttons as you want, but until you add a submit button (maybe change the equals button to a submit button) it won't go anywhere.

In conclusion, you're best off to use javascript in a case such as this - PHP would be a good choice for something where you need to do simple conversions, like fahrenheit to celsius, but for a calculator, where every time a button is pressed something needs to be changed/refreshed, a solution using JavaScript or possibly Ajax would be a better call than PHP.