Simple password confirmation validation using Zend_Validate

PasswordsMatch.php

<?php
class App_Validate_PasswordsMatch extends Zend_Validate_Abstract
{
  const PASSWORD_MISMATCH = 'passwordMismatch';
	
	/**
	 * The field name of the password
	 * 
	 * @var string
	 */
	protected $PasswordField;
	
	/**
	 * The field name of the password confirmation
	 * 
	 * @var string
	 */
	protected $ConfirmField;
	
	/**
	 * @var array
	 */
	protected $_messageTemplates = array(
		self::PASSWORD_MISMATCH => 'Password fields did not match'
	);
	
	/**
	 * Set the field names
	 * 
	 * @param string $passwordField
	 * @param string $confirmField
	 */
	public function __construct($passwordField = 'Password', $confirmField = 'ConfirmPassword', $message = null)
	{
		if(null !== $message) {
			$this->_messageTemplates[self::PASSWORD_MISMATCH] = $message;
		}
		
		$this->PasswordField = $passwordField;
		$this->ConfirmField = $confirmField;
	}
	
	/**
	 * Check the two password field match
	 * 
	 * @param mixed $value
	 * @param array $formContext [optional] The submitted form data
	 * @return boolean
	 * @throws Exception
	 */
	public function isValid($value, $formContext = null)
	{
		if(!isset($formContext[$this->PasswordField]) || 
			!isset($formContext[$this->ConfirmField])) {
			throw new Exception($this->PasswordField . ' or ' . $this->ConfirmField . 
				' not found in ' . __METHOD__);
		}
		
		if($formContext[$this->PasswordField] !== $formContext[$this->ConfirmField]) {
			$this->_error(self::PASSWORD_MISMATCH);
			return false;
		}
		return true;
	}
}