how to input the parent id into database in different table - php

Question

I have table -> subkategori
and I can't insert the id_kategori attribute to table portfolio
i have a code for the model :
function get_subcategories($id_kategori){
$query = $this->db->query("SELECT id_kategori from subkategori WHERE id_subkategori=".$this->input->post('a'));
return $query->result();
}
and the controller here :
if ($this->input->post('a')!=''){
$this->load->model('Model_app');
$this->model_app->get_subcatoegories('$id_kategori');
}else{
$id_kategori = '';
}
$data = array(
'id_subkategori'=>$this->db->escape_str($this->input->post('a')),
'id_kategori'=>$id_kategori
);

Answer 1

$this->input->post('a') as you mentioned here I assume that you have input in the form and its name is a.
In Controller
if (!empty($this->input->post('a')))
{
$this->load->model('Model_app');
$id = $this->model_app->get_subcatoegories($this->input->post('a'));
if (empty($id)) {
$id_kategori = '';
} else {
$id_kategori = $id[0]['id_kategori'];
}
}else{
$id_kategori = '';
}
$data = array(
'id_subkategori'=>$this->db->escape_str($this->input->post('a')),
'id_kategori'=>$id_kategori
);
In Model
function get_subcategories($id_kategori)
{
$query = $this->db->query("SELECT id_kategori FROM subkategori WHERE id_subkategori = $id_kategori");
return $query->result_array();
}
You can get last insterted if with $this->db->insert_id();

Answer 2

In your, if statement you didn't assign the database value to the $id_kategori variable. Hence while inserting the empty value into the table it inserts as 0(int field).
And also when you pass a variable to a function it should not be single quoted. You have to pass the post variable but you are passing a variable which is undefined.
if ($this->input->post('a')!=''){
$this->load->model('Model_app');
$category = $this->model_app->get_subcatoegories($this->input->post('a'));
$id_kategori = $category['id_kategori];
}else{
$id_kategori = '';
}
$data = array(
'id_subkategori'=>$this->db->escape_str($this->input->post('a')),
'id_kategori'=>$id_kategori
);