CodeIgniter:带有WHERE的查询返回错误::$Query=$this->；db->；query(） - CodeIgniter: Query with WHERE returns an error :: $query = $this->db->query()

CodeIgniter: Query with WHERE returns an error :: $query = $this->db->query()

我需要从new_guest表中获取guest_id，其中列guest_nic_pp_dl等于变量guest_nic_pp_dl，LIMIT等于1的结果。然而，我写的代码以一个愚蠢的语法错误结束。如何使用变量值定义WHERE以匹配行？

分析错误：语法错误，第20行上C:''examplep''htdocs''bit''application''models''reservations_model.php中出现意外的"$guest_nic_pp_dl"（T_VARIABLE）

$query = $this->db->query('SELECT guest_id FROM new_guest WHERE guest_nic_pp_dl, '$guest_nic_pp_dl' LIMIT 1'); // Line 20
foreach ($query->result() as $row) {
    return $row->guest_id;

像一样尝试

     $query = $this->db->query("SELECT guest_id FROM new_guest WHERE guest_nic_pp_dl, '$guest_nic_pp_dl' LIMIT 1");

$this->db->select('guest_id');

$this->db->where('guest_nic_pp_dl', $guest_nic_pp_dl);

$this->db->limit(1);

$query = $this->db->get('new_guest');

$query = $this->db->query('SELECT guest_id FROM new_guest WHERE guest_nic_pp_dl='.$guest_nic_pp_dl.' LIMIT 1');
foreach ($query->result() as $row) {
return $row->guest_id;
}