PHP Lecture Notes

Introduction to PHP

• PHP: Server-side scripting language.
• Used to build dynamic web pages.
• Runs on a server, not in the user’s web browser.
• Despite claims it's "dead", PHP is still used by 70% of websites.
• Preferred for its speed, simplicity, and flexibility.
• Often used by freelancers and small businesses.

History of PHP

• Released in 1995.
• Originally "Personal Home Page"; evolved to "PHP: Hypertext Preprocessor".
• Was not originally intended as a full programming language.
• Mascot: An elephant named "Ella".

Basics of PHP

• How PHP Works:
  1. Browser sends request to server.
  2. PHP processes request and accesses any databases.
  3. Server sends back HTML to the browser.
• Commonly used with MySQL, Postgres, Oracle.
• Strongly recommended to have a good foundation in HTML.

Getting Started with PHP

• Recommended setup: XAMPP (Apache + MySQL + PHP)
• Text Editor: Visual Studio Code (VS Code) is popular.

Installation of XAMPP & VS Code

• Go to apachefriends.org.
• Download the correct version for your OS.
• Follow installation prompts, ensuring Apache and MySQL are started.
• Install VS Code from code.visualstudio.com.

Setting up Your First PHP File

• Create a folder under XAMPP's htdocs called website.
• Create index.php as the home page. Code structure:

  <?php
  echo "I like pizza";
  ?>
  

• Run using localhost in the browser.

PHP Code Syntax

• PHP code structure: <?php ... ?>
• Display text using echo "Your message";
• Comments: // for single line, /* ... */ for multi-line.

HTML Integration

• PHP files can contain HTML, CSS, and JavaScript.
• To generate HTML, type ! + tab in VS Code.

Variables in PHP

• Variables are containers for data: e.g. $name = 'SpongeBob';
• Data types include strings, integers, floats, booleans.
• When declaring a variable, always start with a $.

Basic Operations

• Arithmetic operations: +, -, *, /, % (modulus).
• Increment: ++, Decrement: --.

Arrays in PHP

• Arrays store multiple values:

  $fruits = array("apple", "banana", "cherry");
  

• Accessing array elements: $fruits[0] returns "apple".
• Associative arrays use key-value pairs:

  $colors = array("red" => "#FF0000", "green" => "#00FF00");
  

Functions in PHP

• Functions are reusable code blocks:

  function add($a, $b) {
      return $a + $b;
  }
  

• Functions can take parameters and return values.

Including Files

• Use include to add code from external files. This promotes reusability:

  include 'header.php';
  include 'footer.php';
  

Sessions and Cookies

• Cookies: Store user information in the browser.
• Sessions: Store user data on the server for use across multiple pages.
• Use session_start() to begin a session.

Database Connection & MySQL

• Use PHP to connect to MySQL using mysqli_connect().
• Perform SQL operations inside PHP scripts.
• Handle exceptions with try and catch blocks.

SQL Queries

• Inserting and retrieving data from database:

  $sql = "INSERT INTO users (username, password) VALUES ('$username', '$hash')";
  

• Use methods like mysqli_query() to execute SQL queries.

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Practical Exercises and Conclusion

• Create a registration form to insert user data in a database.
• Validate and sanitize user input to avoid security risks.

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Summary

• PHP is a powerful tool for web development.
• Strong understanding of variables, functions, arrays, and SQL is essential for creating dynamic web applications.

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Next Steps

• Continue practicing PHP and SQL integration through hands-on exercises.