feat(): add CsvWriter

CsvWriter.php

@@ -0,0 +1,26 @@
+<?php
+namespace boundstate\importexport;
+
+/**
+ * Writes CSV files.
+ * @package boundstate\importexport
+ */
+class CsvWriter extends BaseWriter
+{
+	/**
+   * Writes to a CSV file.
+   * @return string filename
+   */
+  public function write() {
+    $exporter = $this->source;
+    $filename = \Yii::$app->runtimePath . '/' . uniqid() . '.csv';
+
+    $fp = fopen($filename, 'w');
+
+    foreach ($exporter->export() as $rowNum => $row) {
+      fputcsv($fp, $row);
+    }
+
+    return $filename;
+  }
+}