add conflict management

index.php

@@ -35,9 +35,23 @@
 			function savenote($title, $content)
 			{
 				global $dir;
-				file_put_contents($dir . '/' . $title, $content);
+				$path = $dir . '/' . $title;
+				$lastchanged = filemtime($path);
+				$previous = $_POST['lastchanged'];
+				if ( (int)$lastchanged >  (int)$previous)
+				{
+					$tempcontent = file_get_contents($path);
+					if ($tempcontent != $content)
+					{
+						$temptitle = $title . '_' . $lastchanged;
+						file_put_contents($dir . '/' . $temptitle, $tempcontent);
+						array_unshift($_SESSION['index'], $dir . '/' . $temptitle);
+						echo '<div class="grey">Conflict detected. See backup: ' . $temptitle . '</div>';
+					}
+				}
+				file_put_contents($path, $content);
 				removefromindex($title);
-				array_unshift($_SESSION['index'], $dir . '/' . $title);
+				array_unshift($_SESSION['index'], $path);
 			}
 
 			function linksdiv($content)
@@ -138,6 +152,8 @@
 					$content = file_get_contents($dir . '/' . $title);
 				}
 
+				clearstatcache();
+				$lastchanged = filemtime($dir . '/' . $title);
 				$lines = substr_count($content, "\r\n");
 				$words = substr_count($content, " ") + $lines;
 				$chars = strlen($content);

note.php

@@ -6,6 +6,7 @@
 		<input type="submit" name="links" value="links" accesskey="l">
 		<input type="submit" name="stats" value="stats" accesskey="i">
 		<input type="submit" name="delete" value="delete" accesskey="d">
+		<input hidden name="lastchanged" value="<? echo $lastchanged; ?>">
 		<?php
 		if (isset($_POST['stats']))
 		{