Variables, Data Types & Operators - Concepts
Explore the key concepts of variables, data types & operators with practical examples and exercises.
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
- 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
- Understanding the core principles of variables, data types & operators
- Practical applications and real-world use cases
- Step-by-step implementation guides
- Common patterns and best practices
- Tips for debugging and troubleshooting
- Performance optimization techniques
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 '<'
💡 Missing or extra {}()[] or operator near the error.