VDaemon PHP Library | VDaemon Extension | Table of Contents
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.
VDaemon provides a mechanism for all common types of validation - for example, testing for valid dates or values within a specified range - plus ways to provide custom-written validation. In addition, VDaemon allows for complete customization of 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 VDaemon validation tag (validator) references an input tag on the form. When the user's input is processed (for example, when the form is submitted), VDaemon tests the user's input and sets a state to indicate whether the entry passed the validation test(s). If any of the validation tests fail, the entire form is set to invalid.
You can test the state of a form using your own (custom) code. For example, you can test the state of a form for properly formatted and required information before updating a database with the submitted information. If you detect an invalid state, you bypass the database update. Typically, if any validation check fails, user is returned to the form page with error messages that you have predefined for VDaemon to display in the event of validation failure. These error messages will help to guide and prompt the user to enter the required and/or properly formatted information.
Each VDaemon validator performs just one test. However, you may wish to check an input element for multiple conditions. For example, you might want to establish that a field is required and that it is limited to accepting dates within a specific range. You can have more than one validation tag reference a given input field in a form. In that case, the tests performed by the validators are resolved using a logical AND. The data input by the user must pass all the tests in order to be considered valid.
In some instances, entries in several different formats might be valid. For example, if you are prompting for a phone number, you might allow users to enter a local number, a long-distance number, or an international number. This situation arises primarily when checking for specific patterns of numbers or characters. To perform this type of test — a logical OR — you use the group validator and specify multiple validators within it.
Validators are not visible in the rendered form. However, if the validator detects an error, it produces error message text that you specify. The error message can be displayed in a variety of ways:
Each validator can be referenced by a VDaemon label. VDaemon label displays an error message or glyph in place (usually next to the control where the error occurred).
Validation errors can be collected and displayed in one place - for example, at the top of the form. This strategy is often used in combination with displaying a glyph next to the input fields with errors.
The error message can be different in the summary and in place. You can use this option to show a shorter error message in place with more detail in the summary, or to show an error glyph next to the input field and an error message in the summary.
VDaemon requires PHP version 4.2.0 or later.
This enhanced version of the VDaemon Manual would never come to existance, if the following people would not help with their contribution to the project:
- Daniel Nelson, who made proof reading and added many useful comments
Support can be obtained at:
http://www.x-code.com/vdaemon_web_form_validation.php
vdaemon@x-code.com