Whats wrong with this code?

[rlweb]

<?php

$path = '../../pages/';


// Get file
if (!isset($_GET['file'])) { die('Invalid File'); }
$file = $_GET['file'];

// Create file path
$filepath = $path . $file;



// Get file extension
$ext = explode('.', $file);
$extension = $ext[count($ext)-1];

// Is this file editable or not?
// Check if extension matches an invalid one
$invalid = array('exe', 'doc', 'jpg', 'gif', '');
if (in_array(strtolower($file['extension']), $invalid)) {
    die('Can\'t edit this file. Not suitable for editing. Please go back.');
}

// Form submitted?
if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    // Check if new data has been set
    if (!isset($_POST['newfile'])) {
        die('Please enter some new data for this file.');
    }

    // Write new data
    $f = fopen($filepath, 'w');
    fwrite($f, $_POST['newfile']);
    fclose($f);

    // Redirect
    header ('Location: index.php');
} else {
    // Get file data
    $f = fopen($filepath, 'r');
    $data = fread($f, filesize($filepath));
    fclose($f);

    // Show edit form
    $title = 'Filemanager - Edit File:' . htmlentities($file);
    include ('header.php');
    ?>
    <h2>Edit File: <?php echo htmlentities($file); ?></h2>

    <form method="POST">
        <textarea name="newfile" rows="20" cols="80"><?php echo $data; ?></textarea>
        <br />
        <input type="submit" name="submit" value="Save File" />
    </form>


    <?php
    include ('footer.php');
}

?>

Thanks before hand. The Problem is that the code adds / on every " every time i open the file how can i stop this?

[Heinous]

stripslashes($str);