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1. How PHP Scripts Work (The Lifecycle)

PHP is a server-side scripting language. Unlike client-side languages like JavaScript (which execute entirely inside the user’s browser), PHP processing happens entirely on the web server before the user ever sees a page.

  • Step 1 (Request): A user types a URL into their browser or submits a form, sending an HTTP request to the web server (e.g., Apache or Nginx).
  • Step 2 (Interpreting): The web server recognizes that the requested file ends in .php and passes it to the PHP interpreter (typically managed via PHP-FPM).
  • Step 3 (Execution): The PHP engine executes the code line-by-line. It queries databases, processes data, reads/writes files, and generates raw HTML markup.
  • Step 4 (Response): The PHP engine returns the resulting plain HTML (and CSS/JS output) back to the web server, which sends it as an HTTP response to the client browser. The browser then renders the final web page.

2. Setting Up Basic PHP Development

To write and run PHP code, your local machine needs a development environment consisting of a web server, the PHP interpreter, and optionally a database. Popular options include:

  • All-in-One Local Servers: Tools like XAMPP, WampServer, or MAMP bundle Apache, MySQL, and PHP into a simple installer.
  • Modern Environments: Docker containers (or lightweight toolchains like Laravel Valet on macOS) for emulating exact production servers.

3. Basic PHP Syntax & Core Rules

PHP files typically have a .php extension and can contain text, HTML, CSS, JavaScript, and PHP code tags.

A. PHP Open and Close Tags

The standard and most recommended way to embed PHP code is using the canonical tags:

PHP

<?php
// All PHP code goes inside these delimiters
?>

B. Statements, Case Sensitivity, and Comments

  • Statements: Every instruction in PHP must end with a semicolon (;).
  • Case Sensitivity:
    • Variables are case-sensitive ($userName and $username are two different variables).
    • Functions, classes, and keywords (such as echo, if, while, class) are case-insensitive.
  • Comments: Use // or # for single-line comments, and /* ... */ for multi-line blocks.

C. Variables and Data Types

Variables are declared with a dollar sign ($) followed by the variable name. PHP is a loosely typed language, meaning you don’t need to explicitly declare a variable’s data type.

PHP

<?php
// String
$courseTitle = "Introduction to PHP";

// Integer
$totalLessons = 12;

// Float / Decimal
$completionRate = 95.5;

// Boolean
$isPublished = true;

// Outputting variables using echo
echo "Course: " . $courseTitle . " | Lessons: " . $totalLessons;
?>

Are you looking for recommendations on choosing a specific text editor (like VS Code) or setting up your first local development stack for PHP?