fjerne mellem i fil ved upload

I relation til http://www.eksperten.dk/spm/685381 så har jeg et upload script. Men nu vil jeg gerne have det script til at fjerne mellemrum i den fil som bliver uploadet, da filtræet ikke kan klare mellemrum.

Altså uploadscriptet skal lave "fil navn.fil" om til "filnavn.fil" ved upload.

--- upload script ----

<!-- put all in upload.php -->
<form action="upload.php" method="post" enctype="multipart/form-data">
<span class="style7 style8">Browse a File to Upload: <i>MAXIMUM filesize 10MB.</i></span><br>
<input type="file" name="filetoupload"><br>
<input type="hidden" name="MAX_FILE_SIZE" value="<?echo $size_bytes; ?>">
<br>
<input type="Submit" value="Upload File"><br>
</form>

<?php

/*  Description -----------------------------------------------------
The Super Global Variable $_FILES is used in PHP 4.x.x.
$_FILES['upload']['size'] ==> Get the Size of the File in Bytes.
$_FILES['upload']['tmp_name'] ==> Returns the Temporary Name of the File.
$_FILES['upload']['name'] ==> Returns the Actual Name of the File.
$_FILES['upload']['type'] ==> Returns the Type of the File.

So if I filetoupload the file 'test.doc', the $_FILES['upload']['name']
would be 'phptut.doc' and $_FILES['upload']['type'] would be 'application/msword'.
---------------------------------------------------------------------*/
// this is the upload dir where files will go.
//Don't remove the /
//Chmod it (777)
$upload_dir = "images/";  //change to whatever you want.
// files less than 10MB
$size_bytes = 10485760; //bytes  will be uploaded
//check if the directory exist or not.
if (!is_dir("$upload_dir")) {
    die ("The directory <b>($upload_dir)</b> doesn't exist");
}
//check if the directory is writable.
if (!is_writeable("$upload_dir")){
        die ("The directory <b>($upload_dir)</b> is NOT writable, Please Chmod (777)");
}

//Check first if a file has been selected
//is_filetoupload_file('filename') returns true if
//a file was filetoupload via HTTP POST. Returns false otherwise.
if (is_uploaded_file($_FILES['filetoupload']['tmp_name']))
{

//Get the Size of the File
$size = $_FILES['filetoupload']['size'];
//Make sure that $size is less than 10MB (10000000 bytes)
if ($size > $size_bytes)
{
echo "File Too Large. Please try again.";
exit();

}
// $filename will hold the value of the file name submetted from the form.
$filename =  $_FILES['filetoupload']['name'];
// Check if file is Already EXISTS.
if(file_exists($upload_dir.$filename)){
  echo "<span class='style7 style8'>Oops! The file named <b>$filename </b>already exists </span>";
  exit();
}

//Move the File to the Directory of your choice
//move_filetoupload_file('filename','destination') Moves an filetoupload file to a new location.
if (move_uploaded_file($_FILES['filetoupload']['tmp_name'],$upload_dir.$filename)) {

//tell the user that the file has been filetoupload
echo "<span class='style7 style8'>File (<a href=$upload_dir$filename>$filename</a>) uploaded!</span>";
exit();

}
else
{
//Print error
echo "There was a problem moving your file";
exit();

}
}

?>

/ Simon