codeIgniter 输出 sql 语句，用于测试

<?php
/**
 * CodeIgniter 的测试 Model
 *
 * CodeIgniter 输出 sql 语句代码是：
 * $this->db->last_query()
 */
class TestModel extends CI_Model
{

    private $table = 'DBTable';

    public function index()
    {
        $year  = $this->input->post('year');
        $month = $this->input->post('month');
        $day   = $this->input->post('day');

        $this->load->database();
        $result = $this->db
                       ->select('*')
                       ->from($this->table)
                       ->where('year', $year)
                       ->where('month', $month)
                       ->where('day', $day)
                       ->order_by('sort', 'DESC')
                       ->get()
                       ->rerult();

        // 检查 sql 语句代码                 
        $this->sqlout(__LINE__); 
        
        return $result;
    }

    /* 功能：文件输出 sql 语句代码，用于测试
     *
     * 调用方式：在查询构造器下方输入如下代码
     * $this->sqlout();
     * 
     * 生成的文件目录：applicationmodels
     * 文件名：ClassName_line_sql.txt
     */
    public function sqlout($line)
    {
      $testSql = $this->db->last_query();
      if(isset($testSql)){
            $sql = json_decode(str_replace('
', ' ', json_encode($testSql)));
            file_put_contents(__DIR__.'/'.__CLASS__.'_'.$line.'_sql.txt', $sql);
        }
    }
}

codeIgniter  跳转：redirect(‘signIn/index’);

php 换行符：PHP_EOL