Zend_Validate_PostCode allows you to determine if a given value is a valid postal code. Postal codes are specific to cities, and in some locales termed ZIP codes. Zend_Validate_PostCode knows more than 160 different postal code formates. To select the correct format there are 2 ways. You can either use a fully qualified locale or you can set your own format manually. Using a locale is more convenient as Zend Framework already knows the appropriate postal code format for each locale; however, you need to use the fully qualified locale (one containing a region specifier) to do so. For instance, the locale "de" is a locale but could not be used with Zend_Validate_PostCode as it does not include the region; "de_AT", however, would be a valid locale, as it specifies the region code ("AT", for Austria). When you don't set a locale yourself, then Zend_Validate_PostCode will use the application wide set locale, or, when there is none, the locale returned by Zend_Locale. You can also change the locale afterwards by calling setLocale(). And of course you can get the actual used locale by calling getLocale(). setLocale('en_GB'); ]]> Postal code formats themself are simply regular expression strings. When the international postal code format, which is used by setting the locale, does not fit your needs, then you can also manually set a format by calling setFormat(). setFormat('AT-\d{5}'); ]]> When using self defined formats you should omit the starting ('/^') and ending tags ('$/'). They are attached automatically. You should also be aware that postcode values are always be validated in a strict way. This means that they have to be written standalone without additional characters when they are not covered by the format. At it's most basic, you may pass either a Zend_Locale object or a string representing a fully qualified locale to the constructor of Zend_Validate_PostCode. Additionally, you may pass either an array or a Zend_Config object to the constructor. When you do so, you must include either the key "locale" or "format"; these will be used to set the appropriate values in the validator object. 'de_AT', 'format' => 'AT_\d+' )); ]]> The following options are supported for Zend_Validate_PostCode: format: Sets a postcode format which will be used for validation of the input. locale: Sets a locale from which the postcode will be taken from.