Simple future value calculator problems in php
<p>I'm having trouble understanding why my php program for class is not working. I've looked through a lot of documentation and I think i'm including it right but it says fail to open stream on the include and when I call the function it says it's undefined could someone please point out my probably very simple error here. here is my php page </p>

<pre><code>&lt;!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"&gt;
&lt;?php include 'C:\xampp\htdocs\program1include.php' ?&gt;
&lt;html xmlns="http://www.w3.org/1999/xhtml"&gt;
&lt;head&gt;
&lt;meta http-equiv="Content-Type" content="text/html; charset=utf-8" /&gt;
&lt;title&gt;Future Value Calculator&lt;/title&gt;
&lt;/head&gt;

&lt;body&gt;
&lt;form method="post"&gt;
Principal &lt;input type="text" name="principal" value="&lt;?php if (isset($_POST['principal'])) echo $_POST['principal']; ?&gt;"&gt;&lt;br /&gt;
Interest Rate &lt;input type="text" name="rate" value="&lt;?php if (isset($_POST['rate'])) echo $_POST['rate']; ?&gt;"&gt;&lt;br /&gt;
Years to Invest &lt;input type="text" name="years" value="&lt;?php if (isset($_POST['years'])) echo $_POST['years']; ?&gt;"&gt;&lt;br /&gt;
&lt;input type='submit' name='Submit' value='Get Future Value.' /&gt;&lt;br /&gt;
Future Value:
&lt;?php figureValue(); if(isset($futureValue)){
    echo $futureValue;
}
    else
    {
        echo 'Please Fill Out All Fields.';
    }
?&gt;
&lt;/form&gt;
&lt;/body&gt;
&lt;/html&gt;
</code></pre>

<p>HERE IS THE INCLUDE </p>

<pre><code>&lt;?php 
    function figureValue($principal,$rate,$years){

        $futureValue = round($principal * pow(1 + ($rate/100),
        $years), 2);
    }
    ?&gt;
</code></pre>

<p>the page outputs </p>

<p>Warning: include(C:\xampp\htdocs\program1include.php): failed to open stream: No such file or directory in C:\xampp\htdocs\program1php.php on line 2</p>

<p>Warning: include(): Failed opening 'C:\xampp\htdocs\program1include.php' for inclusion (include_path='.;C:\xampp\php\PEAR') in C:\xampp\htdocs\program1php.php on line 2
Principal 
Interest Rate 
Years to Invest </p>

<p>Future Value: 
Fatal error: Call to undefined function figureValue() in C:\xampp\htdocs\program1php.php on line 16</p>
