limit worksheet length to 31 chars on Moodle 1.5: prevents fatal erro…

…r lib/excel/workbook.php

mod/hotpot/report/default.php

@@ -625,11 +625,13 @@ function print_excel_report(&$course, &$hotpot, &$tables, &$options) {
 			// Moodle >= 1.6
 			require_once("$CFG->libdir/excellib.class.php");
 			$wb = new MoodleExcelWorkbook("-");
+			$wsnamelimit = 0; // no limit
 		} else {
 			// Moodle <= 1.5
 			require_once("$CFG->libdir/excel/Worksheet.php");
 			require_once("$CFG->libdir/excel/Workbook.php");
 			$wb = new Workbook("-");
+			$wsnamelimit = 31; // max length in chars
 		}
 
 		// send HTTP headers
@@ -638,7 +640,16 @@ function print_excel_report(&$course, &$hotpot, &$tables, &$options) {
 		// create one worksheet for each table
 		foreach($tables as $table) {
 			unset($ws);
-			$ws = &$wb->add_worksheet(empty($table->caption) ? '' : strip_tags($table->caption)); 
+			if (empty($table->caption)) {
+				$wsname = '';
+			} else {
+				$wsname = strip_tags($table->caption);
+				if ($wsnamelimit && strlen($wsname) > $wsnamelimit) {
+					$wsname = substr($wsname, -$wsnamelimit); // end of string
+					// $wsname = substr($wsname, 0, $wsnamelimit); // start of string
+				}
+			}
+			$ws = &$wb->add_worksheet($wsname);
 
 			$row = 0;
 			$this->print_excel_head($wb, $ws, $table, $row, $options);