Zend_Validate_Float allows you to validate if a given value contains a floating-point value. This validator validates also localized input. The following options are supported for Zend_Validate_Float: locale: Sets the locale which will be used to validate localized float values. The simplest way to validate a float is by using the system settings. When no option is used, the environment locale is used for validation: isValid(1234.5); // returns true $validator->isValid('10a01'); // returns false $validator->isValid('1,234.5'); // returns true ]]> In the above example we expected that our environment is set to "en" as locale. Often it's useful to be able to validate also localized values. Float values are often written different in other countries. For example using english you will write "1.5". In german you may write "1,5" and in other languages you may use grouping. Zend_Validate_Float is able to validate such notations. But it is limited to the locale you set. See the following code: 'de')); $validator->isValid(1234.5); // returns true $validator->isValid("1 234,5"); // returns false $validator->isValid("1.234"); // returns true ]]> As you can see, by using a locale, your input is validated localized. Using a different notation you get a FALSE when the locale forces a different notation. The locale can also be set afterwards by using setLocale() and retrieved by using getLocale().