Form Validation with Progressive Enhancement: Final Touches

As stated in the preceding segment, in this case the component tasked with validating the data entered in the previous web form will be a simple PHP class not surprisingly called “Validator” (yes, sometimes my creativity with names is really amazing). The underlying logic of this class is very simple to follow. Its corresponding definition looks like this:

(Validator.php)

<?php

class Validator

{

protected $_errors = array();

protected $_errorPrefix = '<p>';

protected $_errorSufix = '</p>';

// check an empty string

public function checkEmpty($value)

{

$value = $this->sanitizeValue($value);

if ($value === '')

{

$this->_errors[] = 'The entered value must be a non-empty string.';

}

return $this;

}

// check an integer number

public function checkInteger($value, array $options = array())

{

$value = $this->sanitizeValue($value);

if (!filter_var($value, FILTER_VALIDATE_INT, $options))

{

$this->_errors[] = 'The value ' . $value . ' must be an integer number.';

}

return $this;

}

// check a float number

public function checkFloat($value, array $options = array())

{

$value = $this->sanitizeValue($value);

if (!filter_var($value, FILTER_VALIDATE_FLOAT, $options))

{

$this->_errors[] = 'The value '. $value . ' must be a float number.';

}

return $this;

}

// check an email address

public function checkEmail($value)

{

$value = $this->sanitizeValue($value);

if (!filter_var($value, FILTER_VALIDATE_EMAIL))

{

$this->_errors[] = 'The value '. $value . ' must be a valid email address.';

}

return $this;

}

// sanitize basically inputted value

protected function sanitizeValue($value)

{

return filter_var(trim($value), FILTER_SANITIZE_STRING);

}

// check the errors

public function validate()

{

return empty($this->_errors);

}

// get the error messages as an array

public function getErrors()

{

return $this->_errors;

}

// get the error messages as a formatted string

public function getFormattedErrors()

{

return $this->_errorPrefix .

implode($this->_errorSufix .

$this->_errorPrefix, $this->_errors) .

$this->_errorSufix;

}

// clean up error messages

public function clearErrors()

{

$this->_errors = array();

}

}

As you can see above, the “Validator” class implements a few discrete methods for checking some typical data types, such as integer and float numbers, empty strings and email addresses. As one might expect, each error that occurs during the validation process is stored on the protected $_errors property, which is used internally by the “validate()” method to determine whether or not the supplied data is correct.

Due to the flexible nature of the class, it’s really easy to extend its current capabilities via additional methods. For demonstration purposes, however, its existing functionality is more than acceptable, so implementing those extra methods will be left as homework for you.

So far, so good. Having defined a class that’s capable of checking some basic data types, we'll now create a script that consumes its API, thus getting the previous form validation program up and running.

This final script will be created in the following section. To get there simply click on the links that appears below and keep reading.