Variables, Data Types & Operators - Concepts
Web accessibility ensures that your websites can be used by everyone, including people with visual, auditory, motor, or cognitive disabilities. Over 1 billion people worldwide live with some form of disability — and when you build inaccessible websites, you are actively excluding them. Beyond ethics, accessibility is also increasingly required by law (ADA, WCAG guidelines) and actually improves your SEO since search engines consume content similarly to screen readers. In this module, you will learn ARIA roles, semantic HTML for accessibility, keyboard navigation, color contrast, and how to test your site with screen readers and accessibility auditing tools
Module Overview & Professional Context
PHP is a server-side scripting language that has powered the web for nearly three decades. First released in 1994 by Rasmus Lerdorf, PHP began as a simple set of Common Gateway Interface (CGI) scripts and evolved into a full-featured general-purpose programming language. Today, PHP 8.x is a modern, high-performance language with an extensive standard library, a thriving ecosystem of packages via Composer, and a wealth of frameworks including Laravel (the most popular PHP framework), Symfony, and WordPress — which alone powers over 43% of all websites on the internet. Despite misconceptions, PHP is actively maintained, regularly updated, and widely used in professional web development. Variables in PHP are dynamically typed — you do not declare a type when creating a variable, and a variable's type can change at runtime. Variables are prefixed with a dollar sign ($): $name = "Alice"; creates a string variable, $age = 25; creates an integer. PHP supports all standard data types: integers (whole numbers), floats (decimal numbers), strings (text), booleans (true/false), arrays (ordered or associative collections), objects (instances of classes), null (the absence of a value), and resources (references to external files or database connections). The gettype() function returns a variable's current type, and the is_string(), is_int(), is_array() family of functions check types explicitly. Type juggling — PHP's automatic type conversion — is powerful but can cause subtle bugs; PHP 8's strict types declaration and the match expression with strict comparison help avoid common pitfalls. Strings in PHP are flexible and powerful. Single-quoted strings are literal — no variable interpolation or escape sequences except for \' and \\. Double-quoted strings support variable interpolation ($name interpolated directly in the string) and escape sequences (\n for newline, \t for tab). Heredoc syntax (<<<EOT) creates multi-line strings with double-quote interpolation behavior. Nowdoc syntax (<<<'EOT') creates multi-line strings with single-quote literal behavior. The concatenation operator (.) joins strings: $greeting = "Hello, " . $name . "!"; String functions form one of PHP's largest standard library sections: strlen() returns character count, strtolower() converts to lowercase, substr() extracts a portion, str_replace() substitutes substrings, explode() splits a string into an array, implode() joins an array into a string, and trim() removes leading and trailing whitespace. Control flow in PHP follows the patterns common to C-family languages. The if/elseif/else conditional executes different code blocks based on boolean expressions. The switch statement matches a value against multiple cases with fall-through behavior unless break is used. The match expression (PHP 8+) is a switch alternative with strict comparison (===), mandatory exhaustiveness checking (throws UnhandledMatchError if no arm matches), and single-expression arms that return values directly. Loops include for (with initialization, condition, and increment), while (condition-first), do-while (condition-last, executes at least once), and foreach (iterates over array elements, perfect for PHP's powerful array type). The continue keyword skips to the next iteration; break exits the loop. Understanding these control flow primitives thoroughly is prerequisite to everything else in PHP development.
Skills & Outcomes in This Module
- Deep conceptual understanding with the 'why' behind each feature
- Practical code patterns used in real enterprise codebases
- Common pitfalls, debugging strategies, and professional best practices
- Integration with adjacent technologies and architectural patterns. Understanding how PHP integrates with the broader ecosystem is essential for building complete, production-ready applications
- Interview preparation: key questions on this topic with detailed answers
- Industry context: where and how these skills are applied professionally
Introduction to Variables, Data Types & Operators
In this section, we cover the fundamental aspects of variables, data types & operators. You'll learn core concepts, see real-world examples, and understand how to apply them in your projects.
Key Concepts
- Deep understanding of variables, data types & operators — not just the syntax and API, but the reasoning behind design decisions, the trade-offs involved, and the historical context that explains why things work the way they do Grasping these fundamentals is essential because they form the backbone of every advanced technique you will learn later
- Practical applications and real-world use cases — a critical concept in server-side web development that you will use frequently in real projects. Each concept is demonstrated with hands-on examples drawn from real-world PHP projects that thousands of developers use daily
- Step-by-step implementation guides — a critical concept in server-side web development that you will use frequently in real projects. Follow along carefully — each step builds on the previous one, creating a solid chain of understanding that will serve you throughout your career
- Common patterns and best practices — a critical concept in server-side web development that you will use frequently in real projects. These patterns have been refined by the developer community over years of experience and are considered industry standards
- Tips for debugging and troubleshooting — a critical concept in server-side web development that you will use frequently in real projects. Debugging is a skill that improves with practice — the tips here come from common real-world issues that even experienced developers encounter
- Performance optimization techniques — a critical concept in server-side web development that you will use frequently in real projects. Writing efficient code is not just about speed — it improves user experience, reduces server costs, and makes your applications feel professional
Variables, Data Types & Operators - Code Example
<?php
// Variables and data types
$name = "Alice";
$age = 25;
$salary = 55000.50;
$isActive = true;
$skills = ["PHP", "MySQL", "JavaScript"];
echo "Name: $name\n";
echo "Age: $age\n";
echo "Type: " . gettype($salary) . "\n";
// String interpolation
echo "Hello, {$name}! You are {$age} years old.\n";
// Type casting
$numStr = "42";
$num = (int)$numStr;
echo "Number: $num\n";
?>Try It Yourself: Variables, Data Types & Operators
Line 1: JS Error: Unexpected token '<'
Tip: Missing or extra {}()[] or operator near the error.