Custom form validation subclass

MY_Form_Validation.php

<?php

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

    /**
     * Error Array
     *
     * This function serves as a getter for the 
     * protected _error_array variable
     *
     * @access	public
     * @return	array
     */
    public function error_array(){
	return $this->error_array();
    }

    /**
     * Add Custom Validation Callback
     * 
     * This method allows a user to set a method or function to be called when a form needs to be validated.
     * 
     * Results from the callback are ignored if they are not an array.
     * 
     * @param str $callback_function the function/method to call (must be public if not a rule in this class)
     * @param str $label the label to be passed (allows better error messages), defaults to an empty string
     * @param mixed $rules the rules to be passed to the function/method, defaults to an empty string
     * @param str $helper the name of the helper to call, if the function is not available in $this context. The helper will be loaded automatically
     * @return bool TRUE if there was post data and the function/method runs, FALSE if there is no POST data
     * @access public
     */	
    public function add_custom_validation_callback($callback_function, $label = '', $rules = '', $helper = ''){

	if(!isset($_POST) || empty($_POST) ){
	    return FALSE; 
	}

	if($helper != ''){
	    $callback_result = $this->_run_callback_from_helper($callback_function, $label, $rules, $helper);
	}else{
	    $callback_result = $this->_run_callback_from_this($callback_function, $label, $rules);
	}

	if(is_array($callback_result)){
	    foreach($callback_result as $error_name=>$error_message){
		$this->_error_array[$error_name] = $error_message;
	    }
	}

	return TRUE;
    }

    protected function _run_callback_from_helper($callback_function, $label, $rules, $helper){
	try{
	    $this->CI->load->helper($helper);

	    if( !function_exists($callback_function) ){
		throw new Exception("The {$callback_function} callback does not exist in the {$helper} helper, or the {$helper} helper could not be loaded.");
	    }else{
		return $callback_function($label, $rules);
	    } 
	}catch (Exception $e){
	    throw new Exception("The {$callback_function} helper callback threw an error: {$e}");
	}
    }

    protected function _run_callback_from_this($callback_function, $label, $rules){
	try{
	    if( !method_exists($this->CI, $callback_function) ){
		throw new Exception("The {$callback_function} callback does not exist in the current context. Did you mean to load it from a helper?");
	    }else{
		return $this->CI->$callback_function($label, $rules);
	    }
	}catch (Exception $e){
	    throw new Exception("The {$callback_function} callback threw an error: {$e}");
	}
    }
    
    
    // --------------------------------------------------------------------
    // More custom validation rules (these rules are for the CodeIgniter
    // set_rules() method, and cannot be called directly for the
    // extended add_custom_validation_callback() method because they return
    // a bool, instead of an error array
    // --------------------------------------------------------------------
   
    /**
     * Valid Student ID (790 or equivelent)
     *
     * @access	public
     * @param	string
     * @return	bool
     */
    public function valid_net_id($str)
    {
	/*
		Explaining the Regex pattern...
		^[a-z]{1,2}   this matches one or two letters at the start (first and last name, or just a last name)
		[0-9]{6}   this requires 6 digits following the initials
		[ega]?     matches the suffix of the netid (currently acceptible are nothing, e, a and g)
	*/
	if( !preg_match( '/^[a-z]{1,2}[0-9]{6}[ega]?$/' , strtolower($str)) ){
	    $this->set_message(__FUNCTION__, 'The %s field must contain a valid NetID');
	    return FALSE;
	}
	return TRUE;	
    }
    
    // --------------------------------------------------------------------
    
    
    /**
     * Valid Student ID (790 or equivelent)
     *
     * @access	public
     * @param	string
     * @return	bool
     */
    public function valid_student_id($str)
    {
	if ( !is_numeric($str) || ($str < 100000000) || ($str > 999999999) )
	{
	    $this->set_message(__FUNCTION__, 'The %s field must contain a valid Student ID number');
	    return FALSE;
	}else{
	    return TRUE;
	}	
    }
    
}