diff --git a/lib/excellib.class.php b/lib/excellib.class.php
index 69e7527..ae07c35 100644
--- a/lib/excellib.class.php
+++ b/lib/excellib.class.php
@@ -122,10 +122,10 @@ class MoodleExcelWorksheet {
      */
     function MoodleExcelWorksheet($name, &$workbook, $latin_output=false) {

-    /// Internally, add one sheet to the workbook
+    /// Internally, add one sheet to the workbook
         $this->pear_excel_worksheet =& $workbook->addWorksheet($name);
         $this->latin_output = $latin_output;
-    /// Set encoding to UTF-16LE
+    /// Set encoding to UTF-16LE
         if (!$this->latin_output) { /// Only if don't want to use latin (win1252) stronger output
             $this->pear_excel_worksheet->setInputEncoding('UTF-16LE');
         }
@@ -177,11 +177,11 @@ class MoodleExcelWorksheet {
      * @param string  $url    The url to write
      * @param mixed   $format The XF format for the cell
      */
-    function write_url($row, $col, $url, $format=null) {
+    function write_url($row, $col, $url, $string='', $format=null) {
     /// Calculate the internal PEAR format
         $format = $this->MoodleExcelFormat2PearExcelFormat($format);
     /// Add  the url safely to the PEAR Worksheet

     /**
@@ -319,7 +319,7 @@ class MoodleExcelWorksheet {
     function hide_screen_gridlines() {
         $this->pear_excel_worksheet->hideScreenGridlines();
     }
-
+
     /**
     * Insert a 24bit bitmap image in a worksheet.
     *
@@ -386,7 +386,7 @@ class MoodleExcelFormat {
      * @param object $workbook The internal PEAR Workbook onject we are creating
      */
     function MoodleExcelFormat(&$workbook, $properties = array()) {
-    /// Internally, add one sheet to the workbook
+    /// Internally, add one sheet to the workbook
         $this->pear_excel_format =& $workbook->addFormat();
     /// If we have something in the array of properties, compute them
         foreach($properties as $property => $value) {