Fix Bug #79296 ZipArchive::open fails on empty file

Author: remicollet

ext/zip/php_zip.c

@@ -1480,6 +1480,21 @@ static ZIPARCHIVE_METHOD(open)
 		ze_obj->filename = NULL;
 	}
 
+#if LIBZIP_VERSION_MAJOR > 1 || LIBZIP_VERSION_MAJOR == 1 && LIBZIP_VERSION_MINOR >= 6
+	/* reduce BC break introduce in libzip 1.6.0
+	   "Do not accept empty files as valid zip archives any longer" */
+
+	/* open for write without option to empty the archive */
+	if ((flags & (ZIP_TRUNCATE | ZIP_RDONLY)) == 0) {
+		zend_stat_t st;
+
+		/* exists and is empty */
+		if (VCWD_STAT(resolved_path, &st) == 0 && st.st_size == 0) {
+			flags |= ZIP_TRUNCATE;
+		}
+	}
+#endif
+
 	intern = zip_open(resolved_path, flags, &err);
 	if (!intern || err) {
 		efree(resolved_path);