Form validation by my own method

You can always extend the Form_validation library and add your custom rules which would be accessible anywhere the form_validation library is used.
http://www.codeigniter.com/user_guide/ge...-libraries

/application/libraries/MY_Form_validation.php

PHP Code:

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

class MY_Form_validation extends CI_Form_validation {
    
    function __construct()
    {
        parent::__construct();
    }

    //a new custom rule
    public function custom_rule($input)
    {
        //$input is the user input for this form field
        if ($input == "hello")
        {
            return TRUE; //passed validation
        } else {
            //Failed! Set error message (using name of rule)
            $this->set_message('custom_rule', 'The %s field can ONLY be "hello".');
        }
        //If we made it this far, we failed. Send FALSE back
        return FALSE;
    }
} 


Then in your controller(s):

PHP Code:

$this->form_validation->set_rules('fieldname', 'field text', 'trim|custom_rule'); 


You can also create rules that receive extra parameters, which are passed in between the [] when setting the rule, like "min[5]". Anything in [] will automatically be passed to your rule definition as a 2nd parameter

PHP Code:

function some_rule($input, $extra = '')
{

} 


if you used:

PHP Code:

$this->form_validation->set_rules('fieldname', 'field text', 'trim|some_rule[something here]'); 


Then $extra will = "something here" in your rule. Useful for passing in extra parameters if you need them (like identifying a db table). Please note that this value will always be a string passed to the rule.

If you look at how they are creating the native rules in the /system/libraries/Form_validation.php, it could be helpful when creating your custom rules.