Identical Zend_Validate_Identical allows you to validate if a given value is identical with an set haystack. Supported options for Zend_Validate_Identical The following options are supported for Zend_Validate_Identical: token: Sets the token with which the input will be validated against. Basic usage To validate if two values are identical you need to set the origin value as haystack. See the following example which validates two strings. isValid($value) { return true; } ]]> The validation will only then return TRUE when both values are 100% identical. In our example, when $value is 'origin'. You can set the wished token also afterwards by using the method setToken() and getToken() to get the actual set token. Identical objects Of course Zend_Validate_Identical can not only validate strings, but also any other variable type like Boolean, Integer, Float, Array or even Objects. As already noted Haystack and Value must be identical. isValid($input)) { // input appears to be valid } else { // input is invalid } ]]> Type comparison You should be aware that also the type of a variable is used for validation. This means that the string '3' is not identical with the integer 3. This is also the case for Form Elements. They are objects or arrays. So you can't simply compare a Textfield which contains a password with an textual password from another source. The Element itself is given as array which also contains additional informations. Configuration As all other validators also Zend_Validate_Identical supports the usage of configuration settings as input parameter. This means that you can configure this validator with an Zend_Config object. But this adds one case which you have to be aware. When you are using an array as haystack then you should wrap it within an 'token' key when it could contain only one element. 123)); if ($valid->isValid($input)) { // input appears to be valid } else { // input is invalid } ]]> The above example validates the integer 123. The reason for this special case is, that you can configure the token which has to be used by giving the 'token' key. So, when your haystack contains one element and this element is named 'token' then you have to wrap it like shown in the example below. array('token' => 123))); if ($valid->isValid($input)) { // input appears to be valid } else { // input is invalid } ]]>