Php – fclose Warning: fclose(): supplied argument is not a valid stream resource

I am getting the warning on my pages

Warning: fclose(): supplied argument is not a valid stream resource

Using the following code

$fp = fopen('data.txt', 'w');
$write = '2';
fwrite($fp, $write);
fclose($fp);  

Update code

if(isset($_REQUEST['go1']))
{
    $fp = fopen('data.txt', 'w');
    $write = '1';
    $fp1 = fopen('file.php', 'w');
    $write1 = '<br><img src="/1/online.png" style="position:absolute; z-index:-2;" />';
}
if(isset($_REQUEST['go2']))
{

    $fp = fopen('data.txt', 'w');
    $write = '2';
    $fp1 = fopen('file.php', 'w');
    $write1 = '<br><img src="/1/offline.png" style="position:absolute; z-index:-2;" />';
}

fwrite($fp, $write);
fclose($fp);
fwrite($fp1, $write1);
fclose($fp1);

$fp = fopen('data.txt', 'r');
$contents = fread($fp, filesize('data.txt'));
fclose($fp);
if($contents == '1')
    include('file.php');
else if($contents == '2')
    include('file.php');
else
    echo 'Something else...';

getting the error on line 27 and line 29
line 27

fclose($fp);    

line29

fclose($fp1);