Attempt to convert the non UTF-8 strings to UTF-8

src/Spout/Writer/CSV/Writer.php

@@ -4,6 +4,7 @@ namespace Box\Spout\Writer\CSV;
 
 use Box\Spout\Writer\AbstractWriter;
 use Box\Spout\Common\Exception\IOException;
+use Box\Spout\Common\Helper\EncodingHelper;
 
 /**
  * Class Writer
@@ -15,7 +16,6 @@ class Writer extends AbstractWriter
 {
     /** Number of rows to write before flushing */
     const FLUSH_THRESHOLD = 500;
-    const BOM_UTF8 = "\xEF\xBB\xBF";
 
     /** @var string Content-Type value for the header */
     protected static $headerContentType = 'text/csv; charset=UTF-8';
@@ -61,7 +61,7 @@ class Writer extends AbstractWriter
     protected function openWriter()
     {
         // Adds UTF-8 BOM for Unicode compatibility
-        $this->globalFunctionsHelper->fputs($this->filePointer, self::BOM_UTF8);
+        $this->globalFunctionsHelper->fputs($this->filePointer, EncodingHelper::BOM_UTF8);
     }
 
     /**