(set_rules method) Add support for 'flash error messages' to CodeIgniter's built in Form Validation library.

MY_Form_validation.php

<?php 

class MY_Form_validation extends CI_Form_validation {

		// --------------------------------------------------------------------

	/**
	 * Set Rules
	 *
	 * This function takes an array of field names, validation
	 * rules as input AND an associative array of rule specific error messages, 
	 * validates the info, and stores it
	 *
	 * @access	public
	 * @param	mixed
	 * @param	string
	 * @param	array
	 * @return	void
	 */
	public function set_rules($field, $label = '', $rules = '', $flash_error_messages = array())
	{
		// No reason to set rules if we have no POST data
		if (count($_POST) == 0)
		{
			return $this;
		}

		// If an array was passed via the first parameter instead of indidual string
		// values we cycle through it and recursively call this function.
		if (is_array($field))
		{
			foreach ($field as $row)
			{
				// Houston, we have a problem...
				if ( ! isset($row['field']) OR ! isset($row['rules']))
				{
					continue;
				}

				// If the field label wasn't passed we use the field name
				$label = ( ! isset($row['label'])) ? $row['field'] : $row['label'];

				// Here we go!
				$this->set_rules($row['field'], $label, $row['rules']);
			}
			return $this;
		}

		// No fields? Nothing to do...
		if ( ! is_string($field) OR  ! is_string($rules) OR $field == '')
		{
			return $this;
		}

		// If the field label wasn't passed we use the field name
		$label = ($label == '') ? $field : $label;

		// Is the field name an array?  We test for the existence of a bracket "[" in
		// the field name to determine this.  If it is an array, we break it apart
		// into its components so that we can fetch the corresponding POST data later
		if (strpos($field, '[') !== FALSE AND preg_match_all('/\[(.*?)\]/', $field, $matches))
		{
			// Note: Due to a bug in current() that affects some versions
			// of PHP we can not pass function call directly into it
			$x = explode('[', $field);
			$indexes[] = current($x);

			for ($i = 0; $i < count($matches['0']); $i++)
			{
				if ($matches['1'][$i] != '')
				{
					$indexes[] = $matches['1'][$i];
				}
			}

			$is_array = TRUE;
		}
		else
		{
			$indexes	= array();
			$is_array	= FALSE;
		}

		// Build our master array
		$this->_field_data[$field] = array(
			'field'						=> $field,
			'label'						=> $label,
			'rules'						=> $rules,
			'is_array'					=> $is_array,
			'keys'						=> $indexes,
			'postdata'					=> NULL,
			'error'						=> '',
			'flash_error_messages'		=> $flash_error_messages
		);

		return $this;
	}


	/**
	 * Executes the Validation routines
	 *
	 * @access	private
	 * @param	array
	 * @param	array
	 * @param	mixed
	 * @param	integer
	 * @return	mixed
	 */
	protected function _execute($row, $rules, $postdata = NULL, $cycles = 0)
	{
		// If the $_POST data is an array we will run a recursive call
		if (is_array($postdata))
		{
			foreach ($postdata as $key => $val)
			{
				$this->_execute($row, $rules, $val, $cycles);
				$cycles++;
			}

			return;
		}

		// --------------------------------------------------------------------

		// If the field is blank, but NOT required, no further tests are necessary
		$callback = FALSE;
		if ( ! in_array('required', $rules) AND is_null($postdata))
		{
			// Before we bail out, does the rule contain a callback?
			if (preg_match("/(callback_\w+(\[.*?\])?)/", implode(' ', $rules), $match))
			{
				$callback = TRUE;
				$rules = (array('1' => $match[1]));
			}
			else
			{
				return;
			}
		}

		// --------------------------------------------------------------------

		// Isset Test. Typically this rule will only apply to checkboxes.
		if (is_null($postdata) AND $callback == FALSE)
		{
			if (in_array('isset', $rules, TRUE) OR in_array('required', $rules))
			{
				// Set the message type
				$type = (in_array('required', $rules)) ? 'required' : 'isset';

				if ( ! isset($this->_error_messages[$type]) && ! isset($row['flash_error_messages'][$type]))
				{
					if (FALSE === ($line = $this->CI->lang->line($type)))
					{
						$line = 'The field was not set';
					}
				}
				else
				{
					if(isset($row['flash_error_messages'][$type])){
						$line = $row['flash_error_messages'][$type];
					}
					else 
					{
						$line = $this->_error_messages[$rule];
					}	
				}

				// Build the error message
				$message = sprintf($line, $this->_translate_fieldname($row['label']));

				// Save the error message
				$this->_field_data[$row['field']]['error'] = $message;

				if ( ! isset($this->_error_array[$row['field']]))
				{
					$this->_error_array[$row['field']] = $message;
				}
			}

			return;
		}

		// --------------------------------------------------------------------

		// Cycle through each rule and run it
		foreach ($rules As $rule)
		{
			$_in_array = FALSE;

			// We set the $postdata variable with the current data in our master array so that
			// each cycle of the loop is dealing with the processed data from the last cycle
			if ($row['is_array'] == TRUE AND is_array($this->_field_data[$row['field']]['postdata']))
			{
				// We shouldn't need this safety, but just in case there isn't an array index
				// associated with this cycle we'll bail out
				if ( ! isset($this->_field_data[$row['field']]['postdata'][$cycles]))
				{
					continue;
				}

				$postdata = $this->_field_data[$row['field']]['postdata'][$cycles];
				$_in_array = TRUE;
			}
			else
			{
				$postdata = $this->_field_data[$row['field']]['postdata'];
			}

			// --------------------------------------------------------------------

			// Is the rule a callback?
			$callback = FALSE;
			if (substr($rule, 0, 9) == 'callback_')
			{
				$rule = substr($rule, 9);
				$callback = TRUE;
			}

			// Strip the parameter (if exists) from the rule
			// Rules can contain a parameter: max_length[5]
			$param = FALSE;
			if (preg_match("/(.*?)\[(.*)\]/", $rule, $match))
			{
				$rule	= $match[1];
				$param	= $match[2];
			}

			// Call the function that corresponds to the rule
			if ($callback === TRUE)
			{
				if ( ! method_exists($this->CI, $rule))
				{
					continue;
				}

				// Run the function and grab the result
				$result = $this->CI->$rule($postdata, $param);

				// Re-assign the result to the master data array
				if ($_in_array == TRUE)
				{
					$this->_field_data[$row['field']]['postdata'][$cycles] = (is_bool($result)) ? $postdata : $result;
				}
				else
				{
					$this->_field_data[$row['field']]['postdata'] = (is_bool($result)) ? $postdata : $result;
				}

				// If the field isn't required and we just processed a callback we'll move on...
				if ( ! in_array('required', $rules, TRUE) AND $result !== FALSE)
				{
					continue;
				}
			}
			else
			{
				if ( ! method_exists($this, $rule))
				{
					// If our own wrapper function doesn't exist we see if a native PHP function does.
					// Users can use any native PHP function call that has one param.
					if (function_exists($rule))
					{
						$result = $rule($postdata);

						if ($_in_array == TRUE)
						{
							$this->_field_data[$row['field']]['postdata'][$cycles] = (is_bool($result)) ? $postdata : $result;
						}
						else
						{
							$this->_field_data[$row['field']]['postdata'] = (is_bool($result)) ? $postdata : $result;
						}
					}
					else
					{
						log_message('debug', "Unable to find validation rule: ".$rule);
					}

					continue;
				}

				$result = $this->$rule($postdata, $param);

				if ($_in_array == TRUE)
				{
					$this->_field_data[$row['field']]['postdata'][$cycles] = (is_bool($result)) ? $postdata : $result;
				}
				else
				{
					$this->_field_data[$row['field']]['postdata'] = (is_bool($result)) ? $postdata : $result;
				}
			}

			// Did the rule test negatively?  If so, grab the error.
			if ($result === FALSE)
			{

				if ( ! isset($this->_error_messages[$rule]) && ! isset($row['flash_error_messages'][$type]))
				{
					if (FALSE === ($line = $this->CI->lang->line($rule)))
					{
						$line = 'Unable to access an error message corresponding to your field name.';
					}
				}
				else
				{
					if(isset($row['flash_error_messages'][$rule])){
						$line = $row['flash_error_messages'][$rule];
					}
					else 
					{
						$line = $this->_error_messages[$rule];
					}	
				}

				// Is the parameter we are inserting into the error message the name
				// of another field?  If so we need to grab its "field label"
				if (isset($this->_field_data[$param]) AND isset($this->_field_data[$param]['label']))
				{
					$param = $this->_translate_fieldname($this->_field_data[$param]['label']);
				}

				// Build the error message
				$message = sprintf($line, $this->_translate_fieldname($row['label']), $param);

				// Save the error message
				$this->_field_data[$row['field']]['error'] = $message;

				if ( ! isset($this->_error_array[$row['field']]))
				{
					$this->_error_array[$row['field']] = $message;
				}

				return;
			}
		}
	}
}