codeigniter Check if data exist in database update table row - php

Question

How to check if a column exists in query builder Codeigniter 3?
my database table name is "tags" and this table have two column (post_id and tag) here is my code to add tags to post:
//add post tags
public function add_post_tags($post_id)
{
//tags
$tags = trim($this->input->post('tags', true));
$tags_array = explode(",", $tags);
if (!empty($tags_array)) {
foreach ($tags_array as $tag) {
$tag = trim($tag);
if (strlen($tag) > 1) {
$data = array(
'post_id' => $post_id,
'tag' => trim($tag),
'tag_slug' => str_slug(trim($tag))
);
if (empty($data["tag_slug"]) || $data["tag_slug"] == "-") {
$data["tag_slug"] = "tag-" . uniqid();
}
//insert tag
$this->db->insert('tags', $data);
}
}
}
}
I want to check if data exists in the database update the post_id column if not exist insert new data
"post_id" column like "5,8,9"
I want to add the post number to the previous numbers when I update "post_id" column
for example after update "post_id" column This table is like this "5,8,9,11" here 11 is my last post id

Answer 1

Try using replace() instead :
$this->db->replace('tags', $data);
Basically it inserts a new record if it doesn't exist, it updates it according to its primary or unique key if it does exist.