HTML form with PHP

[lucerias]

I am currently create a calculator and then completed the HTML form interface with fields and labels but now i have no idea how to click on the calculate button and then it will call PHP to do the calculation and then pass back the value and display on the html form field? Please provide a simple code sample. Thank you so much.

[lucerias]

May i know the meaning of action of form?

[fert]

action refers the user to the script that will handle the form data. example:
[code]
<form method="post" action="script.php">
[/code]

[Skatecrazy1]

this has been tested and works:
[code]
<?php  $self = $_SERVER['PHP_SELF'];
          $operator = $_POST['radio'];
          $value1 = $_POST['value1'];
          $value2 = $_POST['value2'];
if(isset($operator)){
  if($operator == "*"){
    $final_value = $value1 * $value2;
  }
  elseif($operator == "/"){
    $final_value = $value1 / $value2;
  }
  elseif($operator == "+"){
    $final_value = $value1 + $value2;
  }
  elseif($operator == "-"){
    $final_value = $value1 - $value2;
  }
} else {
    $final_value = "";
}

?>

<form method="post" action="<?php echo $self; ?>">
First Value <input type="text" name="value1" />
<br />
+ <input type="radio" name="radio" value="+" />
- <input type="radio" name="radio" value="-" />
x <input type="radio" name="radio" value="*" />
/ <input type="radio" name="radio" value="/" />
<br />
Second Value <input type="text" name="value2" />
<br />
<input type="submit" value="Calculate" />
<br /><br />
Final Value: <input type="text" value="<?php echo $final_value; ?>" />
</form>
[/code]