codeigniter in number of rows in php code example

Example 1: codeigniter count rows

$this->db
  ->where(['field'=>'foo'])
  ->from("tablename")
  ->count_all_results();

//OR 
$this->db
  ->where(['field'=>'foo'])
  ->count_all_results("tablename");

Example 2: get result count codeigniter

public function record_count() {
   return $this->db->count_all("tablename");
}