HomePHP Page 4 - Building An Extensible Form Validator Class
How Things Work - PHP
Wondering what OOP can do for you? Well, wonder no more - thisarticle demonstrates how OOP can save you time and effort by building aPHP-based Form Validator object to validate HTML form input. In additionto a detailed walkthrough of the process of constructing a PHP class totest user input, this article also includes usage examples and a brieflook at some powerful open-source alternatives.
Now, before proceeding further, I need to decide how this class is going to work. Here's how I plan to use it:
// some form processor
// let's assume that the variables $a and $b
// have been obtained via a form POST operation
// create an object
$fv = new FormValidator();
// run validation methods
// the first argument is the name of the field to validate
// the second is the error to report if validation fails
$fv->isString("a", "Please enter a string for field A");
// same here
$fv->isNumber("b", "Please enter a string for field B");
// check to see error status
As you can see, I would like to call class methods with two
parameters: the name of the form variable to validate, and the error message to return in the event the validation test fails. With this in mind, it becomes much easier to design the class appropriately.
Once the basic functionality of the class is clear, it's a good idea to spend some time listing the important methods, together with their purpose. Here's my initial cut:
isEmpty($var, $errormsg) - check whether the specified form variable is empty;
isString($var, $errormsg) - check whether the specified form variable contains string data;
isNumber($var, $errormsg) - check whether the specified form variable contains numeric data;
isWithinRange($var, $errormsg) - check whether the specified form variable contains a value within the specified numeric range;
isEmailAddress($var, $errormsg) - check whether the specified form variable contains a valid email address;
isError() - check whether any errors have occurred in form validation;
getErrorList() - return the list of validation errors;
resetErrorList() - reset the error list.
These are the essential methods; there may be more, which I will add as development progresses.