<?php

class MY_Form_validation extends CI_Form_validation
{
    private $_custom_field_errors = array();

    public function _execute($row, $rules, $postdata = NULL, $cycles = 0)
    {
        // Execute the parent method from CI_Form_validation.
        parent::_execute($row, $rules, $postdata, $cycles);

        // Override any error messages for the current field.
        if (isset($this->_error_array[$row['field']])
            && isset($this->_custom_field_errors[$row['field']]))
        {
            $message = str_replace(
                '%s',
                !empty($row['label']) ? $row['label'] : $row['field'],
                $this->_custom_field_errors[$row['field']]);

            $this->_error_array[$row['field']] = $message;
            $this->_field_data[$row['field']]['error'] = $message;
        }
    }

    public function set_rules($field, $label = '', $rules = '', $message = '')
    {
        $rules = parent::set_rules($field, $label, $rules);

        if (!empty($message))
        {
            $this->_custom_field_errors[$field] = $message;
        }

        return $rules;
    }
}

?>

CodeIgniter’s models may be added to autoload.php (which will always load them even if they’re not required) or must be manually loaded using code such as:

$this->load->model('views\account\logon');

While it’s only one line of code, it soon becomes tedious having to have a similar line across every action in every controller. Consequently, I created a CodeIgniter library (after taking inspiration from Doctrine’s ClassLoader) which uses spl_autoload. Class_loader automates the process of loading classes within a defined namespace and only requires a single line of configuration; therefore no changes to autoload.php or manual calls to load are required.

Class_loader.php:

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

/**
 * Class_loader is a CodeIgniter library which uses SPL autoload to
 * automatically include classes within the defined namespace.
 * 
 * @author Andrew Mackrodt <andrew@ajmm.org>
 * @version 2011.06.23
 */
class Class_loader
{
    /**
     * @param string $namespace The namespace to apply the autoloader.
     * @param string $includePath
     *     The parent folder of the root namespace. Defaults to CodeIgniter's
     *     APPPATH if no value is given.
     */
    public function register($namespace, $includePath = null)
    {
        if (!empty($namespace) && $namespace[0] == '\\')
        {
            // Strip leading namespace separator.
            $namespace = substr($namespace, 1);
        }

        if (empty($includePath))
        {
            // Set the include path to the CI application folder.
            $includePath = APPPATH;
        }

        // Ensure the include path ends with the OS directory separator.
        $includePath = rtrim($includePath, '\\/').DIRECTORY_SEPARATOR;

        // Register the auto-loader.
        $classLoader = new _ClassLoader($namespace, $includePath);
        spl_autoload_register(array($classLoader, 'loadClass'));
    }
}

/**
 * A helper class to be used by Class_loader. 
 */
class _ClassLoader
{
    private $namespace;
    private $includePath;

    public function __construct($namespace = null, $includePath = null)
    {
        $this->namespace = $namespace;
        $this->includePath = $includePath;
    }

    public function loadClass($className)
    {
        if ($this->namespace !== null
                && strpos($className, $this->namespace.'\\') !== 0)
        {
            return false;
        }
        
        // Convert a namespace to a path using the OS directory separator.
        $classPath = str_replace(array('\\', '/'), DIRECTORY_SEPARATOR, $className);
        
        require_once $this->includePath.$className.'.php';
        return true;
    }
}

Usage:

The classes you wish to autoload must contain a namespace and be located appropriately, e.g. I have a Script class which is located at APPPATH/models/views/shared/Script.php and has the namespace models\views\shared.

$this->class_loader->register('models\views', APPPATH);