CodeIgniter unique validator that has support for excluding a specific row.

MY_Form_validation.php

public function unique($value, $params)
{
    $CI =& get_instance();
    list($table, $field, $exclude_field, $exclude_value) = array_pad(explode('.', $params, 4), 4, NULL);
    
    $CI->form_validation->set_message('unique', 'The %s that you requested is unavailable.');

    $CI->db->select('COUNT(*) AS dupe')->from($table)->where($field, $value)->limit(1);
    if($exclude_field AND $exclude_value)
    {
        $CI->db->select($exclude_field . ' AS id');
        $CI->db->where($exclude_field . ' !=', $exclude_value);
    }

    $row = $CI->db->get()->row();
    return ($row->dupe > 0) ? FALSE : TRUE;
}

Usage

Check for total uniqueness:

unique[table.field]

Check if unique but exclude row where field user_id is 40 from. This is handy for checking uniqueness when you want to update a row.

unique[table.field.user_id.40]