Internet Programming 622 Study Hub

1.2 GET vs POST

The form action says where the data goes. The form method says how it is sent. The guide presents GET as suitable for small amounts of data because values appear in the URL. POST sends data in the request body and is better when more data or more sensitive data is involved.

1.6 Dynamic Forms and Validation

The guide describes a PHP-generated form that checks missing required fields, highlights errors, keeps previous values, and shows a thank-you message only after successful validation.

• processForm() checks submitted required fields.
• displayForm($missingFields) redisplays the form with feedback.
• setValue(), setChecked(), and setSelected() preserve user input.
• validateField() marks missing fields for styling.

$missing = [];
foreach (["name", "email", "age"] as $field) {
	if (empty($_POST[$field])) {
		$missing[] = $field;
	}
}

2.3 Sessions

Sessions store persistent variables on the server and link them to a user through a session ID. PHP commonly stores that ID in a browser cookie called PHPSESSID.

session_start();

$_SESSION["hits"] = ($_SESSION["hits"] ?? 0) + 1;
echo "This page has been viewed " . $_SESSION["hits"] . " times.";

• session_start() loads or creates the session.
• $_SESSION holds session values.
• session_id() gets the current session ID.
• session_destroy() destroys session data.

2.5 Combining Cookies and Sessions

The guide explains that temporary state can live in a PHP session, while longer-term identity or preference state can be stored in a cookie and then used to retrieve persistent data.

if (isset($_POST["bgcolor"])) {
	setcookie("bgcolor", $_POST["bgcolor"], time() + 60 * 60 * 24 * 7);
}

$background = $_COOKIE["bgcolor"] ?? $_POST["bgcolor"] ?? "gray";

3.3 Reading and Writing

Use the function that matches the job: whole-file reads for small files, line-by-line reads for logs or CSV data, and pointer-based reads when you need exact positions.

$handle = fopen("data.txt", "a");
if ($handle) {
	fwrite($handle, "New line" . PHP_EOL);
	fclose($handle);
}

3.5 Working With Directories

Directory handles work like file handles. Open the directory, read each entry, skip . and .., then close the handle.

$handle = opendir("files_dir");
if ($handle) {
	while (($file = readdir($handle)) !== false) {
		if ($file !== "." && $file !== "..") {
			echo htmlspecialchars($file) . "<br>";
		}
	}
	closedir($handle);
}

4.3 CRUD SQL

CRUD means create, read, update, and delete. In this guide, the fruit table is used to demonstrate the core SQL statements.

INSERT INTO fruit (name, color) VALUES ('banana', 'yellow');

SELECT * FROM fruit;
SELECT name, color FROM fruit WHERE id >= 2;

UPDATE fruit
SET name = 'grapefruit', color = 'yellow'
WHERE id = 2;

DELETE FROM fruit WHERE id = 2;

4.4 Connecting PHP to MySQL

The guide explains mysqli and PDO, then shows procedural mysqli connection and query examples. Always check the connection and query result before processing rows.

$conn = mysqli_connect("localhost", "root", "", "mydatabase");

if (!$conn) {
	die("Connection failed: " . mysqli_connect_error());
}

$result = mysqli_query($conn, "SELECT * FROM fruit");
if (!$result) {
	die("Query failed: " . mysqli_error($conn));
}

while ($row = mysqli_fetch_assoc($result)) {
	echo "<li>A " . htmlspecialchars($row["name"]) .
		" is " . htmlspecialchars($row["color"]) . "</li>";
}

mysqli_close($conn);

5.2 Run PHP

Create a folder inside htdocs, open that folder in your editor, save files with a .php extension, start Apache in XAMPP, then access the page through the browser.

<?php
echo "<h1>My Name is Derek</h1>";
?>