Unit 5: PHP and MYSQL
Part 1: PHP Basics
PHP (Hypertext Preprocessor) is a server-side scripting language. PHP code is executed on the server, and the result is returned to the browser as plain HTML.
1. Arrays
Arrays store multiple values in a single variable.
- Indexed Arrays: Numeric keys (0, 1, 2…).
- Associative Arrays: Named keys (like a dictionary).
- Multidimensional Arrays: Arrays containing other arrays.
<?php
// Indexed Array
$cars = array("Volvo", "BMW", "Toyota");
echo $cars[0]; // Outputs: Volvo
// Associative Array (Key => Value)
$ages = array("Peter"=>"35", "Ben"=>"37", "Joe"=>"43");
echo $ages['Peter']; // Outputs: 35
// Loop through Associative Array
foreach($ages as $name => $age) {
echo "$name is $age years old.<br>";
}
?>2. Functions
Blocks of code that can be used repeatedly.
<?php
// Function with parameters and return value
function addNumbers(int $a, int $b) {
return $a + $b;
}
echo addNumbers(5, 10); // Outputs: 15
?>3. Form Handling
PHP uses superglobals $_GET and $_POST to collect form data.
- POST: Secure, invisible to others (data sent in HTTP body). used for passwords/sensitive info.
- GET: Data is visible in the URL (e.g.,
page.php?id=10). Used for bookmarks/search queries.
<form method="post" action="<?php echo $_SERVER['PHP_SELF'];?>">
Name: <input type="text" name="fname">
<input type="submit">
</form>
<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
// Collect value of input field
$name = htmlspecialchars($_REQUEST['fname']);
if (empty($name)) {
echo "Name is empty";
} else {
echo "Hello $name";
}
}
?>4. File Handling
Reading and writing files on the server.
fopen(): Opens a file. Modes:r(read),w(write/overwrite),a(append).fread(): Reads content.fclose(): Closes the file (crucial for freeing resources).
<?php
$myfile = fopen("webdictionary.txt", "r") or die("Unable to open file!");
echo fread($myfile, filesize("webdictionary.txt"));
fclose($myfile);
?>5. Date and Time
The date() function formats a timestamp to a readable date and time.
<?php
echo "Today is " . date("Y/m/d") . "<br>"; // 2023/10/25
echo "The time is " . date("h:i:sa"); // 08:15:30pm
?>Part 2: MySQL Basics & Connectivity
MySQL is the database system used to store information. PHP needs a way to “talk” to MySQL.
1. Database Connectivity (The Modern Way)
We use the mysqli (MySQL Improved) extension. It supports both Procedural and Object-Oriented styles.
Connecting to the Database:
<?php
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "myDB";
// 1. Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// 2. Check connection
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
echo "Connected successfully";
?>2. Executing SQL Queries
Once connected, you use $conn->query($sql) to run SQL commands (INSERT, UPDATE, DELETE, SELECT).
Selecting Data:
$sql = "SELECT id, firstname, lastname FROM MyGuests";
$result = $conn->query($sql);
if ($result->num_rows > 0) {
// Output data of each row
while($row = $result->fetch_assoc()) {
echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. "<br>";
}
} else {
echo "0 results";
}
$conn->close();
?>Part 3: Advanced Web Features
1. Sessions ($_SESSION)
A session stores user information on the server to be used across multiple pages (e.g., keeping a user logged in).
- Note:
session_start()must be the very first thing in your document, before any HTML tags.
<?php
session_start();
// Set session variables
$_SESSION["favcolor"] = "green";
$_SESSION["username"] = "JohnDoe";
// Access on another page
echo "User is " . $_SESSION["username"];
// Destroy session (Logout)
session_unset();
session_destroy();
?>2. Cookies ($_COOKIE)
Cookies are small text files stored on the client’s computer (browser).
- Used for remembering preferences (e.g., Light/Dark mode).
<?php
// setcookie(name, value, expire, path);
$cookie_name = "user";
$cookie_value = "John Doe";
// Cookie expires in 30 days (86400 seconds * 30)
setcookie($cookie_name, $cookie_value, time() + (86400 * 30), "/");
// Check if cookie is set
if(isset($_COOKIE[$cookie_name])) {
echo "User is " . $_COOKIE[$cookie_name];
}
?>3. Sending E-mail
PHP uses the mail() function. (Note: This requires a configured SMTP server, like Sendmail or Postfix, on your hosting environment).
<?php
$to = "somebody@example.com";
$subject = "My Subject";
$txt = "Hello world!";
$headers = "From: webmaster@example.com";
mail($to, $subject, $txt, $headers);
?>Part 4: Integration (XML & AJAX)
1. PHP and XML
PHP provides the SimpleXML extension to parse XML files easily.
Scenario: You have a file note.xml.
<?php
$xml = simplexml_load_file("note.xml") or die("Error: Cannot create object");
// Accessing nodes like object properties
echo $xml->to . "<br>";
echo $xml->from . "<br>";
echo $xml->body;
?>2. PHP and AJAX
This is the most powerful combination in modern web dev.
- Frontend (JS): Sends a request.
- Backend (PHP): Receives the request, processes data (maybe queries MySQL), and outputs the result.
The PHP File (gethint.php - The Backend):
This script listens for a GET request and simply outputs text.
<?php
// Get the 'q' parameter from URL
$q = $_REQUEST["q"];
$hint = "";
// Logic: lookup all hints from array if $q is different from ""
if ($q !== "") {
$q = strtolower($q);
$len = strlen($q);
// (Imagine a $a array of names exists here)
foreach($a as $name) {
if (stristr($q, substr($name, 0, $len))) {
if ($hint === "") {
$hint = $name;
} else {
$hint .= ", $name";
}
}
}
}
// Output the response
echo $hint === "" ? "no suggestion" : $hint;
?>The AJAX Request (Frontend):
function showHint(str) {
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
document.getElementById("txtHint").innerHTML = this.responseText;
}
};
// Calls the PHP file
xhttp.open("GET", "gethint.php?q=" + str, true);
xhttp.send();
}