echo implode (",", $array) question

I have this little script to scan a directory of images. I want to write the image names into a javascript array.

I almost have it, but the problem is I get a trailing comma after the last item in the array.

So, is there a way to use implode instead of the way I did it?

<?PHP
  // filetypes to display
  $imagetypes = array("image/jpeg", "image/gif");
?>
    <?PHP
  // Original PHP code by Chirp Internet: www.chirp.com.au
  // Please acknowledge use of this code by including this header.

  function getImages($dir)
  {
    global $imagetypes;

    // array to hold return value
    $retval = array();

    // add trailing slash if missing
    if(substr($dir, -1) != "/") $dir .= "/";

    // full server path to directory
    $fulldir = "{$_SERVER['DOCUMENT_ROOT']}/$dir";

    $d = @dir($fulldir) or die("getImages: Failed opening directory $dir for reading");
    while(false !== ($entry = $d->read())) {
      // skip hidden files
      if($entry[0] == ".") continue;

      // check for image files
      if(in_array(mime_content_type("$fulldir$entry"), $imagetypes)) {
        $retval[] = array(
         "file" => "/$dir$entry",
         "size" => getimagesize("$fulldir$entry")
        );
      }
    }
    $d->close();

    return $retval;
  }
?>
    <?PHP
  // fetch image details
  $images = getImages("webDesign");

  
  
  
  // display on page
  echo "<script>var imgArr = [";
  foreach($images as $img) {
    
    echo   "\"{$img['file']}\",\n"; // this is giving me a trailing comma
   
    //echo implode (",\n ", $images); // this is returning [Array, Array, Array...]
    }
  echo "]</script>";
?>

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