A server-side scripting language built specifically for the web, still powers a huge share of it (WordPress alone accounts for a large fraction of all websites).

Setup

php -v
php -S localhost:8000     # built-in dev server, no Apache/Nginx needed locally

Install Composer (the package manager) for anything beyond a single script:

curl -sS https://getcomposer.org/installer | php
php composer.phar init

Core syntax

<?php

$name = "Ada";
$count = 0;

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

// arrays (both indexed and associative use the same type)
$nums = [1, 2, 3];
$user = ["name" => "Ada", "age" => 30];

echo "Hello, {$user['name']}!\n";

// classes
class Animal {
    public function __construct(private string $name) {}
    public function speak(): string {
        return "{$this->name} makes a sound.";
    }
}

$dog = new Animal("Rex");
echo $dog->speak();

Control flow & match

$grade = 85;

$letter = match (true) {
    $grade >= 90 => "A",
    $grade >= 80 => "B",
    $grade >= 70 => "C",
    default => "F",
};

match (PHP 8+) uses strict comparison and has no fallthrough, unlike switch, prefer it for value-mapping logic.

Working with a database (PDO)

$pdo = new PDO("mysql:host=localhost;dbname=app", "user", "pass");
$stmt = $pdo->prepare("SELECT * FROM users WHERE id = ?");
$stmt->execute([$id]);
$user = $stmt->fetch(PDO::FETCH_ASSOC);

Always use prepared statements (? placeholders), string-concatenating user input into SQL is the classic PHP injection vector.

Popular frameworks

A tiny Laravel route (for context)

Route::get('/users/{id}', function ($id) {
    return User::findOrFail($id);
});

Laravel's Eloquent ORM (User::findOrFail($id)) replaces most raw PDO code above in real applications.

Common gotchas

• == performs type juggling ("abc" == 0 was true before PHP 8, and some looser comparisons still surprise people), prefer ===.
• Array functions are inconsistent about parameter order (in_array($needle, $haystack) vs array_map($callback, $array)), there's no shortcut but experience; keep the docs open.
• Superglobals ($_GET, $_POST, $_SESSION) are global mutable state, modern frameworks wrap them in request objects for a reason; avoid touching them directly outside small scripts.