codeigniter: closure table - add descendant - php

Question

I'm trying to add a new descendant, but having difficulties achieving it, it displays some error, Would be grateful if you could take time to review what I've done thus far.
Here's
Controller
public function index() {
$this->load->view('closure_view');
}
public function add() {
$add_new = array(
'ancestor' => $this->input->post('ancestor'),
'descendant' => $this->input->post('descendant'),
'lvl' => $this->input->post('lvl'),
'id' => $this->input->post('id')
);
$cust_id = $this->closure->add($add_new);
redirect('http://localhost/kgmerchant/index.php/welcome');
}
Model
public $table;
public $closure_table = 'closures';
public function __construct($table_name = NULL, $closure_table = NULL){
parent::__construct();
$this->table = $table_name;
if ($closure_table !== NULL) {
$this->closure_table = $closure_table;
}
}
public function add($node_id, $target_id = 0) {
$sql = 'SELECT ancestor, '.$node_id.', lvl+1
FROM '.$this->closure_table.'
WHERE descendant = '.$target_id.'
UNION
SELECT '.$node_id.','.$node_id.',0';
$query = 'INSERT INTO '.$this->closure_table.' (ancestor, descendant, lvl) ('.$sql.')';
$result = $this->db->query($query);
return $result;
}
View
<form name="home" method="post" action="<?php echo base_url().'index.php/home/add' ?>" >
<input placeholder="ancestor" type="text" name="ancestor" required/>
<input placeholder="descendant" type="text" name="descendant" required/>
<input placeholder="lvl" type="text" name="lvl" required />
<input placeholder="id" type="hidden" name="id" value="" />
<input type="submit" value="Okay" />
</form>
Thanks.
Error
Message: Array to string conversion

Answer 1

Your model can't be called "Closure" because that's a reserved name in PHP. Change the name to something else and it should work.