Don't delete photo when used elsewhere

php/modules/Photo.php

@@ -210,12 +210,15 @@ class Photo extends Module {
 
 	}
 
-	private function exists($checksum) {
+	private function exists($checksum, $photoID = null) {
 
 		# Check dependencies
 		self::dependencies(isset($this->database, $checksum));
 
-		$query	= "SELECT id, url, thumbUrl FROM lychee_photos WHERE checksum = '$checksum' LIMIT 1;";
+		# Exclude $photoID from select when $photoID is set
+		if (isset($photoID)) $query = "SELECT id, url, thumbUrl FROM lychee_photos WHERE checksum = '$checksum' AND id <> '$photoID' LIMIT 1;";
+		else $query = "SELECT id, url, thumbUrl FROM lychee_photos WHERE checksum = '$checksum' LIMIT 1;";
+
 		$result	= $this->database->query($query);
 
 		if (!$result) {
@@ -820,7 +823,7 @@ class Photo extends Module {
 		$this->plugins(__METHOD__, 0, func_get_args());
 
 		# Get photos
-		$photos = $this->database->query("SELECT id, url, thumbUrl FROM lychee_photos WHERE id IN ($this->photoIDs);");
+		$photos = $this->database->query("SELECT id, url, thumbUrl, checksum FROM lychee_photos WHERE id IN ($this->photoIDs);");
 		if (!$photos) {
 			Log::error($this->database, __METHOD__, __LINE__, $this->database->error);
 			return false;
@@ -829,6 +832,10 @@ class Photo extends Module {
 		# For each photo
 		while ($photo = $photos->fetch_object()) {
 
+			# Check if other photos are referring to this images
+			# If so, only delete the db entry
+			if ($this->exists($photo->checksum, $photo->id)===false) {
+
 				# Get retina thumb url
 				$thumbUrl2x = explode(".", $photo->thumbUrl);
 				$thumbUrl2x = $thumbUrl2x[0] . '@2x.' . $thumbUrl2x[1];
@@ -851,6 +858,8 @@ class Photo extends Module {
 					return false;
 				}
 
+			}
+
 			# Delete db entry
 			$delete = $this->database->query("DELETE FROM lychee_photos WHERE id = '$photo->id';");
 			if (!$delete) {