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Let's cover Unit 6: PHP and MySQL concisely, focusing on the core concepts for your oral
exam.

Unit 6: PHP and MySQL (05) - Concise Overview

PHP (Hypertext Preprocessor) is a widely-used open-source server-side scripting language
primarily designed for web development. It's often embedded directly into HTML and is highly
compatible with databases like MySQL.

1. Introduction to PHP5 and PHP6 (and PHP 7+/8+)

• PHP Basics: PHP code is executed on the server, and the resulting HTML (or other output)
is sent to the client's browser. It's known for its simplicity and strong integration with
databases.
• PHP5: A major version that introduced significant features for object-oriented programming
(OOP) such as robust object models, interfaces, abstract classes, exception handling, and
improved performance. It was widely used for many years.
• PHP6: This version was initially planned to focus heavily on Unicode support. However,
development stalled, and it was ultimately never officially released due to various
challenges and disagreements within the community. The planned features were instead
integrated into subsequent PHP 5.x releases and eventually into PHP 7.
• PHP 7+ (and PHP 8+): These are the truly significant successors to PHP 5. PHP 7
introduced a new Zend Engine which brought dramatic performance improvements (2x-3x
faster than PHP 5.6), along with new features like scalar type declarations, return type
declarations, the null coalescing operator, and anonymous classes. PHP 8 continued this
trend with JIT compilation, Union Types, Attributes, and more.
• For your exam: Be aware that PHP6 was a "skipped" version in the public release
cycle. Focus on PHP5's OOP features and the major performance/feature leaps in
PHP 7/8.

2. Variables and Constants

• Variables:
• Used to store data.
• Always start with a dollar sign ($).
• No explicit type declaration needed (dynamically typed).
• Case-sensitive (e.g., $name is different from $Name).
• Example: $name = "Alice";, $age = 30;
• Constants:
• Values that cannot be changed during script execution.
 • Defined using the define() function or the const keyword (PHP 5.3+ for class
constants, PHP 5.6+ for global constants outside classes).
• Typically named in uppercase.
• Example: define("PI", 3.14);, const MAX_SIZE = 100;

3. Program Flow
Controls the order in which statements are executed.
• Conditional Statements:
• if, else if, else: Execute code based on a condition.
• switch: Execute different blocks of code based on a single value.
• Looping Statements:
• for: Loops a specific number of times.
• while: Loops as long as a condition is true.
• do...while: Loops at least once, then as long as a condition is true.
• foreach: Specifically for iterating over arrays.
• Control Statements:
• break: Exits a loop or switch statement.
• continue: Skips the rest of the current loop iteration and proceeds to the next.

4. Functions
• Basics: Reusable blocks of code that perform a specific task.
• Definition: Declared using the function keyword.
• Parameters & Arguments: Functions can accept input values (parameters) and return a
value.
• Return Value: return keyword sends a value back from the function.
• User-defined Functions: Functions created by the developer.
• Built-in Functions: PHP provides a vast library of pre-defined functions (e.g., strlen(),
date(), explode(), isset()).
• Example:
PHP
<?php
function greet($name) {
return "Hello, " . $name . "!";
}
echo greet("World"); // Output: Hello, World!
?>

5. Arrays and Files and Directories

• Arrays:
• Variables that can hold multiple values.
 • Indexed Arrays: Numeric keys (e.g., [0], [1]). array("apple",
"banana")
• Associative Arrays: Named keys (strings). array("name" => "John",
"age" => 30)
• Multidimensional Arrays: Arrays containing other arrays.
• Example: $fruits = ["apple", "banana"];, $person = ["name"
=> "Jane", "age" => 25];
• Files and Directories:
• PHP has extensive built-in functions for interacting with the file system.
• File Operations:
• Opening: fopen() ('r' for read, 'w' for write, 'a' for append).
• Reading: fread(), fgets(), file_get_contents().
• Writing: fwrite(), file_put_contents().
• Closing: fclose().
• Checking existence: file_exists().
• Directory Operations:
• Creating: mkdir().
• Deleting: rmdir().
• Reading contents: scandir().
• Example (reading a file):
PHP
<?php
$filename = "data.txt";
if (file_exists($filename)) {
$content = file_get_contents($filename);
echo $content;
} else {
echo "File not found!";
}
?>

6. Forms and Databases

• Forms:
• PHP is crucial for processing HTML forms submitted by users.
• $_GET: A superglobal array used to collect data sent with the GET method (data
appears in the URL query string).
• $_POST: A superglobal array used to collect data sent with the POST method (data
is sent in the HTTP request body, not visible in URL). Preferred for sensitive data or
large submissions.
• Form Validation: PHP is used for server-side validation to ensure data integrity and
security, preventing malicious input.
• Example (processing a POST form):
PHP
<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
 $username = $_POST["username"];
$email = $_POST["email"];
echo "Username: " . htmlspecialchars($username) . "<br>";
echo "Email: " . htmlspecialchars($email);
// Further validation and database insertion
}
?>
<form method="POST">
Username: <input type="text" name="username"><br>
Email: <input type="email" name="email"><br>
<input type="submit" value="Submit">
</form>

• Databases:
• PHP is widely used to interact with databases to store, retrieve, update, and delete
data.
• MySQL: A popular open-source relational database management system (RDBMS)
that integrates seamlessly with PHP.

7. Integration with MySQL Applications on PHP

Connecting PHP applications to MySQL databases is a common practice for dynamic web content.
• Database Extensions: PHP provides extensions to interact with MySQL:
• MySQLi (MySQL Improved Extension): The recommended modern procedural or
object-oriented interface for MySQL. Supports prepared statements (for security and
performance).
• PDO (PHP Data Objects): A database abstraction layer that supports multiple
databases (MySQL, PostgreSQL, SQLite, etc.) using a unified interface. Also
supports prepared statements.
• (Note: The old mysql_ functions are deprecated and should not be used.)
• Connection:
• Establishing a connection to the MySQL server (host, username, password, database
name).
• Error handling for connection failures.
• Implementation of CRUD Operations (with MySQLi/PDO):
• CREATE (Insert):
• SQL: INSERT INTO users (name, email) VALUES (?, ?)
• PHP: Prepare statement, bind parameters, execute.
• READ (Select):
• SQL: SELECT * FROM users WHERE id = ?
• PHP: Prepare statement, bind parameters, execute, fetch results (e.g.,
fetch_assoc(), fetch()).
• UPDATE:
• SQL: UPDATE users SET email = ? WHERE id = ?
• PHP: Prepare statement, bind parameters, execute.
• DELETE:
 • SQL: DELETE FROM users WHERE id = ?
• PHP: Prepare statement, bind parameters, execute.
• Prepared Statements (Crucial for Security):
• Essential for preventing SQL Injection attacks.
• The SQL query structure is sent to the database separately from the actual data. The
database then compiles the query and binds the data, ensuring the data is treated as
values, not executable code.
• Example (MySQLi for SELECT):
PHP
<?php
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "mydb";

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);

// Check connection
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}

// Prepare statement (READ operation)

$stmt = $conn->prepare("SELECT id, name, email FROM users WHERE id =
?");
$user_id = 1;
$stmt->bind_param("i", $user_id); // "i" for integer
$stmt->execute();
$result = $stmt->get_result();

if ($result->num_rows > 0) {
while($row = $result->fetch_assoc()) {
echo "ID: " . $row["id"]. " - Name: " . $row["name"]. " -
Email: " . $row["email"]. "<br>";
}
} else {
echo "0 results";
}
$stmt->close();
$conn->close();
?>

Concise Practice Questions (Unit 6: PHP and MySQL)

1. What was the fate of PHP6, and what major improvements did PHP7 introduce over PHP5?
2. How do variables and constants differ in PHP syntax and behavior?
3. Name two looping constructs in PHP and provide a scenario where foreach would be
particularly useful.
4. Explain the purpose of $_GET and $_POST superglobals in PHP form handling. Which one
is generally safer for sensitive data and why?
5. Why is using prepared statements (with MySQLi or PDO) crucial when integrating PHP
with MySQL databases?
 6. Outline the basic steps involved in performing a "Read" (SELECT) operation from a
MySQL database using PHP.
7. Give two examples of built-in file system functions in PHP.
Sources

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