Merge pull request #5447 from keller31/patch-1

BOM 头应该放到文件头部输出

src/Grid/Exporters/CsvExporter.php

@@ -160,7 +160,7 @@ public function export()
         $response = function () {
             $handle = fopen('php://output', 'w');
             $titles = [];
-
+            fwrite($handle, chr(0xEF).chr(0xBB).chr(0xBF)); //导出的CSV文件是无BOM编码UTF-8，而我们通常使用UTF-8编码格式都是有BOM的。所以添加BOM于CSV中
             $this->chunk(function ($collection) use ($handle, &$titles) {
                 Column::setOriginalGridModels($collection);
 
@@ -170,7 +170,7 @@ public function export()
                     $current = $column->fill($current);
                     $this->grid->columnNames[] = $column->getName();
                 });
-                fwrite($handle, chr(0xEF).chr(0xBB).chr(0xBF)); //导出的CSV文件是无BOM编码UTF-8，而我们通常使用UTF-8编码格式都是有BOM的。所以添加BOM于CSV中
+
                 // Write title
                 if (empty($titles)) {
                     fputcsv($handle, $titles = $this->getVisiableTitles());