Zend_Validate_Digits validates if a given value contains only digits. There are no additional options for Zend_Validate_Digits: To validate if a given value contains only digits and no other characters, simply call the validator like shown in this example: isValid("1234567890"); // returns true $validator->isValid(1234); // returns true $validator->isValid('1a234'); // returns false ]]> When you want to validate numbers or numeric values, be aware that this validator only validates digits. This means that any other sign like a thousand separator or a comma will not pass this validator. In this case you should use Zend_Validate_Int or Zend_Validate_Float.