file_writer.php

<?php
class Sample
{
    private $fp;

    public function __construct($local_filepath)
    {
        $this->fp = fopen($local_filepath, 'w');
        if ($this->fp === false) {
            throw new \Exception(__METHOD__ . " filepath: $local_filepath への書き込みに失敗しました");
        }
    }

    public function send(array $row)
    {
        return fputcsv($this->fp, $row);
    }

    public function close()
    {
        fclose($this->fp);
    }
}