Exercise : Regex validation (by Morgan Doocy)

Adapt the solution to Exercise 1 (Buggy HTML Form) to create a PHP script with form validation.

Make the form self-submitting (i.e., submit back to the same PHP script).
Using regular expressions, ensure the following conditions are met:
1. The uwnetid value must be exactly 8 (eight) acceptable characters: alphabetic, numeric, an underscore ('_'), or a dash ('-').
2. The year value must be one of the four accepted values.
3. The studentid value must be exactly 7 (seven) numeric characters.
4. The essay value should have between 450 and 550 words. Assume a word is a sequence of one or more alphabetic or numeric characters. To account for punctuation and spacing, assume that words are separated by anything that isn’t alphabetic or numeric.

Exercise : Regex validation, continued

If any validation fails, display an error message. Otherwise, display a thank-you message containing at least one of the values submitted.
Note that each of the values must consist of the patterns specified on the previous page, and nothing else.

Exercise solution

<?php
	$valid = true;
	if ($_SERVER['REQUEST_METHOD'] == 'POST') {
		$patterns = array(
			'uwnetid' => '/^[a-z_\-]{8}$/i',
			'year' => '/^frosh|soph|junior|senior$/',
			'studentid' => '/^\d{7}$/',
			'essay' => '/^[a-z0-9]+([^a-z0-9]+[a-z0-9]+){449,549}$/'
		);
		foreach ($patterns as $param => $pattern) {
			if (!isset($_POST[$param]) || !preg_match($pattern, $_POST[$param])) {
				$valid = false;
				break;
			}
		}
	}
?>

Exercise solution, continued

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>Essay Submission</title>
	</head>
	<body>
		<?php if ($_SERVER['REQUEST_METHOD'] == 'GET') { ?>
			<form action="" method="post">
				<!-- (form controls here) -->
			</form>
		<?php } else if ($_SERVER['REQUEST_METHOD'] == 'POST') { ?>
			<?php if (!$valid) { ?>
				<p>ERROR: You submitted an invalid value.</p>
			<?php } else { ?>
				<p>Thank you for your submission, <?= $_POST['uwnetid'] ?>!</p>
			<?php } ?>
		<?php } ?>
	</body>
</html>