Having defined validation in this way provides the foundation for
Zend_Validate_Interface, which defines two methods,
isValid() and getMessages(). The
isValid() method performs validation upon the provided
value, returning TRUE if and only if the value passes
against the validation criteria.
If isValid() returns FALSE, the
getMessages() returns an array of messages explaining
the reason(s) for validation failure. The array keys are short
strings that identify the reasons for validation failure, and the
array values are the corresponding human-readable string messages.
The keys and values are class-dependent; each validation class
defines its own set of validation failure messages and the unique
keys that identify them. Each class also has a const
definition that matches each identifier for a validation failure
cause.
Note
The getMessages() methods return validation
failure information only for the most recent
isValid() call. Each call to
isValid() clears any messages and errors caused by
a previous isValid() call, because it's likely
that each call to isValid() is made for a
different input value.
The following example illustrates validation of an e-mail address:
<?php
$validator = new Zend_Validate_EmailAddress();
if ($validator->isValid($email)) {
// email appears to be valid
} else {
// email is invalid; print the reasons
foreach ($validator->getMessages() as $messageId => $message) {
echo "Validation failure '$messageId': $message\n";
}
}