Getting Started with PHP 8 — PHP 8: Modern PHP Development

PHP 8 (8.0 in 2020 through 8.4/8.5 today) turned PHP into a modern, strongly typed language with a JIT, union types, enums, attributes, readonly properties and more. Check your version with php -v, list loaded extensions with php -m, and find the active configuration with php --ini.

For local development you can run the built-in web server (php -S localhost:8000 -t public); in production PHP runs behind PHP-FPM with Nginx or Apache. Start every file with declare(strict_types=1); so scalar type declarations are enforced instead of silently coercing values.

<?php
declare(strict_types=1);

function greet(string $name, int $times = 1): string
{
    return str_repeat("Hello, {$name}! ", $times);
}

echo greet('Ada', 2), PHP_EOL;   // Hello, Ada! Hello, Ada!
// greet('Ada', '2');            // TypeError with strict_types=1

Useful commands

Command	Purpose
`php -v`	PHP version
`php -m`	Loaded extensions
`php --ini`	Which php.ini files are loaded
`php -S localhost:8000 -t public`	Built-in dev server
`php -l file.php`	Syntax check (lint)

Common pitfalls

Forgetting declare(strict_types=1) — it must be the very first statement and applies per file (to calls made from that file).
Using the built-in server in production; it's single-threaded and meant for development only.
Editing the wrong php.ini: CLI and FPM often load different files.

Key points

PHP 8 is a modern, typed language with a JIT
Enable strict types in every file
Use the built-in server only for development

Further reading: PHP manual: strict typing

Practice questions

What does declare(strict_types=1) change?

Answer

It makes scalar type declarations strict for calls made from that file: passing '5' to an int parameter throws a TypeError instead of being coerced. It doesn't affect return-value coercion in other files and must be the first statement in the file.

Why might php -i and a web page show different settings?

Answer

The CLI SAPI and PHP-FPM usually load different php.ini files and extensions. Use php --ini for the CLI and phpinfo() (temporarily, never in production) or FPM configuration to check the web SAPI.