An important aspect of creating Web Forms pages for user input is to be able to check that the information users enter is valid. VDaemon is a PHP library that grants an easy-to-use but powerful way to check for errors and, if necessary, display messages to the user. VDaemon provides several custom HTML tags (VDaemon tags) to allow developer define form validation rules and some PHP functions to define validation behavior. VDaemon is intended for web developers who have at least basic PHP experience. / VDaemon gives mechanism for all common types of standard validation - for example, testing for valid dates or values within a range - plus ways to provide custom-written validation. In addition, VDaemon allow you to completely customize how error information is displayed to the user. / You enable validation of user input by adding VDaemon tags to your form as you would with other HTML tags. Each validation tag references an input tag on the form. When the user's input is being processed (for example, when the form is submitted), the VDaemon tests the user's input and set a state to indicate whether the entry passed the test. If any of validation checks failed, the entire form is set to invalid. / You can test the state of the form in your own code. For example, you would test the state of form before updating a database with information entered by the user. If you detect an invalid state, you bypass the update. Typically, if any validation checks fail, you skip all your own processing and return the page to the user. VDaemon then produce an error message that appears on the page. / | 
