Merge pull request #2761 from PHPOffice/Reduce-Size-of-Cell-Collection-Unique-ID

Reduce size of Unique ID Prefix used for the Cell Collection

Author: MarkBaker

src/PhpSpreadsheet/Collection/Cells.php

@@ -6,6 +6,7 @@
 use PhpOffice\PhpSpreadsheet\Cell\Cell;
 use PhpOffice\PhpSpreadsheet\Cell\Coordinate;
 use PhpOffice\PhpSpreadsheet\Exception as PhpSpreadsheetException;
+use PhpOffice\PhpSpreadsheet\Settings;
 use PhpOffice\PhpSpreadsheet\Worksheet\Worksheet;
 use Psr\SimpleCache\CacheInterface;
 
@@ -298,7 +299,9 @@ public function getHighestRow($column = null)
      */
     private function getUniqueID()
     {
-        return uniqid('phpspreadsheet.', true) . '.';
+        return Settings::getCache() instanceof Memory
+            ? random_bytes(7) . ':'
+            : uniqid('phpspreadsheet.', true) . '.';
     }
 
     /**