The PHP Handbook – Learn PHP for Beginners

PHP is one of the most popular programming languages for web development. It powers over 75% of all websites on the internet, including large sites like Facebook, Wikipedia, and WordPress. If you want to become a web developer, learning PHP is a great place to start.

In this comprehensive guide, we‘ll cover everything you need to know to start programming in PHP. Whether you‘re a complete beginner or have some experience with other languages, this handbook will help you get up to speed quickly. Let‘s dive in!

What is PHP?

First, let‘s define what PHP is. PHP originally stood for "Personal Home Page", but now stands for "PHP: Hypertext Preprocessor". It is a server-side scripting language that allows you to create dynamic websites and web applications.

When a web browser requests a web page ending in .php, the web server processes the PHP code and sends the output as HTML to the browser. Unlike static HTML pages, PHP can generate different content each time a page loads. It can pull information from a database, process form data submitted by a user, handle user authentication and sessions, and much more.

Some advantages of using PHP for web development include:

• It‘s open source and free to use
• It has a gentle learning curve compared to some other languages
• It‘s platform independent and can run on Windows, Mac, Linux
• It integrates well with HTML
• It has a huge ecosystem of frameworks, libraries, and tools
• It offers excellent documentation and community support

Setting Up a PHP Development Environment

Before you can start writing PHP code, you‘ll need to set up a development environment on your local machine. Here are the basic components you‘ll need:

• A web server program like Apache or Nginx to serve your PHP pages
• The PHP engine itself to process your code
• Optionally, a database like MySQL or PostgreSQL if your application needs one

The easiest way to set this up is to install a pre-configured stack like XAMPP, MAMP or WAMP depending on your operating system. These packages include everything you need in a single install.

For example, to install XAMPP on Windows:

1. Download the XAMPP installer from apachefriends.org
2. Run the installer and choose the components you want (at minimum Apache, PHP, and MySQL)
3. Open the XAMPP control panel and start the Apache and MySQL services
4. Navigate to localhost in your web browser. If you see the XAMPP splash page, it worked!

You can now add your PHP files to the htdocs directory (e.g. C:\xampp\htdocs) and view them at localhost/yourfile.php.

PHP Language Basics

Now that your environment is ready, let‘s look at some PHP code! A PHP script can be placed anywhere in an HTML document. It always starts with <?php and ends with ?>

Here‘s the obligatory Hello World in PHP:

<?php
echo "Hello World!";
?>

The echo statement outputs one or more strings to the page.

Variables and Data Types

Variables in PHP start with a $ sign followed by the variable name. They are loosely typed, meaning you don‘t have to specify the data type. PHP supports the following data types:

• String – sequences of characters
• Integer – whole numbers
• Float – decimal numbers
• Boolean – true or false
• Array – lists of key/value pairs
• Object – instances of classes
• NULL – a special type for a variable with no value

Here are some examples of declaring variables:

<?php
$name = "Alice";
$age = 30;
$score = 94.5;
$is_student = true;
$courses = array("Math", "Science", "History");
?>

Operators

PHP has the standard arithmetic, assignment, comparison and logical operators you find in most languages:

• Arithmetic: +, -, *, /, % (modulo)
• Assignment: =, +=, -=, *=, /=
• Comparison: ==, ===, !=, !==, >, <, >=, <=
• Logical: && (and), || (or), ! (not)

Examples:

<?php
$x = 10;
$y = 5;

echo $x + $y; // 15
echo $x % $y; // 0

if($x > $y) {
echo "$x is greater than $y";
}
?>

Control Structures

PHP has the usual control structures for conditionals and loops:

• if, else, elseif – executes code based on one or more conditions
• switch – alternative to if-elseif when comparing a value to many possibilities
• while – loops through a block as long as a condition is true
• do-while – like while but always runs at least once
• for – loops through a block a specified number of times
• foreach – loops through each element in an array

Example of if-else:

<?php
$age = 20;

if($age >= 21) {
echo "You can drink";
} else {
echo "You cannot drink";
}
?>

Example of a for loop:

<?php
for($i=0; $i<=10; $i++) {
echo $i . "
";
}
?>

This will print the numbers 0 to 10.

Functions

Functions allow you to group reusable pieces of code together. You define a function with the function keyword, followed by the function name, parameters and code block:

<?php
function sayHello($name) {
echo "Hello $name!";
}

sayHello("John"); // outputs Hello John!
?>

PHP has many useful built-in functions for strings, numbers, arrays, dates, and more. For example:

<?php
$string = "Hello World";
echo strlen($string); // outputs 11

$number = 49;
$square_root = sqrt($number);
echo $square_root; // outputs 7

$array = array("red", "green", "blue");
array_push($array, "yellow");
print_r($array);
/ outputs:
Array
(
[0] => red
[1] => green
[2] => blue
[3] => yellow
)
/
?>

Classes and Objects

PHP has support for object-oriented programming with classes and objects. A class is a template for an object. It can have properties (variables) and methods (functions).

<?php
class Car {
public $color;
public $model;

public function __construct($color, $model) {
$this->color = $color;
$this->model = $model;
}

public function message() {
return "My car is a " . $this->color . " " . $this->model . "!";
}
}

$myCar = new Car("black", "Volvo");
echo $myCar -> message();
?>
This will output: My car is a black Volvo!

The public keyword specifies that the property or method can be accessed from outside the class. There are also protected and private access modifiers.

The __construct() function is a special method that is called when an object is created.

Working with Forms

One of the most common uses of PHP is processing HTML forms. When a form is submitted to a PHP script, the form data is available in the $_POST or $_GET superglobal arrays, depending on the form method attribute.

Here‘s an example HTML form:

Name:
E-mail:

And here‘s the welcome.php script that handles the form:

<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
$name = test_input($_POST["name"]);
$email = test_input($_POST["email"]);

echo "Welcome $name, your email is $email";
}

function test_input($data) {
$data = trim($data);
$data = stripslashes($data);
$data = htmlspecialchars($data);
return $data;
}
?>

This script first checks if the form was submitted using POST. If so, it retrieves the name and email fields from the $_POST array, passing them through the test_input() function to strip any malicious characters. Finally, it outputs a welcome message with the submitted data.

Working with Databases

Most real-world PHP applications interact with a database to store and retrieve data. PHP supports many popular databases including MySQL, PostgreSQL, Oracle, and Microsoft SQL Server.

To connect to a MySQL database, you can use the mysqli extension. Here‘s a basic example:

<?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);
}

$sql = "SELECT name, email FROM users";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
// output data of each row
while($row = $result->fetch_assoc()) {
echo "Name: " . $row["name"]. " – Email: " . $row["email"]. "
";
}
} else {
echo "0 results";
}

$conn->close();
?>

This script establishes a connection to a MySQL database using the mysqli object. It then performs a SELECT query to retrieve all rows from the users table. The results are fetched in a while loop and printed to the page. Finally, the database connection is closed.

Using Composer Packages

Composer is a dependency manager for PHP that allows you to declare and manage the libraries your project depends on. Instead of manually downloading and including library files, you can use Composer to automatically install and update them.

To use Composer:

1. Install Composer from getcomposer.org
2. Create a composer.json file in your project root describing your dependencies. For example:
   {
   "require": {
   "monolog/monolog": "1.0.*"
   }
   }
3. Run composer install. This will download the specified packages into a vendor directory.
4. Include the Composer autoloader in your PHP scripts:

require ‘vendor/autoload.php‘;

Now you can use the installed packages in your code. Composer has a vast repository of PHP packages available at packagist.org.

Deploying PHP Applications

Once your PHP application is ready, you‘ll want to deploy it to a web server so others can access it. There are many ways to deploy PHP:

• Shared Hosting – cheapest option, uploads your files via FTP to a shared server
• Virtual Private Server (VPS) – more flexible but requires more setup and maintenance
• Platform as a Service (PaaS) – providers like Heroku or DigitalOcean App Platform handle deployment and scaling for you

Whichever method you choose, be sure to:

1. Upload all application files
2. Ensure file permissions are correctly set (web server needs read access, and write access for any files it needs to modify)
3. Configure your database connection details
4. Change any URLs from localhost to your domain
5. Set up SSL for security
6. Enable caching and optimize performance where possible

A popular deployment approach is to use a version control system like Git to push changes to your server. Many hosting providers support this workflow.

Conclusion

We‘ve only scratched the surface of what‘s possible with PHP, but hopefully this guide has given you a solid foundation to start from. Some key takeaways:

• PHP is a powerful and approachable language for web development
• It has a wide range of uses from small scripts to large applications
• Understanding the basics of syntax, data types, control structures and functions is essential
• Forms and databases are key components of dynamic websites
• Tools like Composer can greatly enhance your workflow
• Deploying your code is the final step to launching your PHP projects to the world

The best way to truly learn PHP is by practice. Think of a project idea and start building! Consult the PHP manual and other online resources when you get stuck. With some patience and persistence, you‘ll be a proficient PHP programmer in no time.