thp-web/md/learn/index.md

Welcome

Welcome to the documentation of the THP programming languague.

THP is a new programming language that compiles to PHP.

This page discusses some of the design decitions of the language, if you want to install THP go to the installation guide

If you want to learn the language, go to the learn section.

Goals

• Bring static typing to PHP: Not just type hints, not use mixed for everything that isn't a primitive type.
• Avoid automatic type conversion.
• Remove the inconsistencies in the language.
• Organize the stdlib.
• Differentiate between Arrays, Tuples, Maps and Sets.
• Create a consistent language.
• Create typings for popular libraries (like TS's .d.ts).
• Have a simple instalation and configuration (requiring just Composer).
• Ship a fast, native binary (written in Rust) (why use PHP when we can go native?).
• Sub 10ms watch mode.
• Support in-place compilation.
• Emit readable PHP code.
• Implement a LSP server.

Not goals

These are not aspects that THP looks to solve or implement.

• Be what TypeScript is for JavaScript (PHP with types).
• Use PHP syntax/conventions.
• Be familiar for PHP developers.

Philosophy

• Consistency over familiarity
• Change over conventions
• Explicit over implicit

Some differences with PHP

// PHP
$has_key = str_contains($haystack, 'needle');

// THP
let has_key = haystack.contains("needle")

• Explicit variable declaration
• No $ for variable names (and thus no $$variable)
• No semicolons
• Use methods on common datatypes
• Strings use only double quotes

---

// PHP
[
    'names' => ['Toni', 'Stark'],
    'age' => 33,
    'numbers' => [32, 64, 128]
]

// THP
Obj {
    names: #("Toni", "Stark"), // Tuple
    age: 33,
    numbers: [32, 64, 128]
}

• Tuples, Arrays, Sets, Maps are clearly different
• JS-like object syntax

---

// PHP
$cat = new Cat("Michifu", 7);
$cat->meow();

// THP
let cat = Cat("Michifu", 7)
cat.meow();

• No new for classes
• Use dot . instead of arrow -> syntax

---

// PHP
use \Some\Deeply\Nested\Class
use \Some\Deeply\Nested\Interface

// THP
use Some::Deeply::Nested::{Class, Interface}

• Different module syntax
• Explicit module declaration
• PSR-4 required
• No include, include_once, require or require_once

---

Other things:

• Pattern matching
• ADTs

Runtime changes

Where possible THP will compile to available PHP functions/classes/methods/etc.

For example:

// This expression
let greeting = 
    match get_person()
    | Some(person) if person.age > 18
    { 
        "Welcome, {person.name}"
    }
    | Some(person)
    {
        "I'm sorry {person.name}, you need to be 18 or older"
    }
    | None
    {
        "Nobody is here"
    }


// Would compile to:
$greeting = null;
$_person = get_person();
if ($_person !== null) {
    if ($_person["age"] > 18) {
        $greeting = "Welcome, " . $_person["name"];
    }
    else {
        $greeting = "I'm sorry " . $_person["name"] . ", you need to be 18 or older";
    }
}
else {
    $greeting = "Nobody is here";
}

However, more advanced datatypes & helper functions will require a sort of runtime (new classes/functions/etc) or abuse the language's syntax/semantics.

// TBD: Enum compilation
enum IpAddress {
    V4(String),
    V6(String),
}

let ip_1 = IpAddress::V4("255.255.0.0")


// Would possibly compile to:
enum IpAddress {
    V4,
    V6,
}

$ip_1 = [IpAddress::V4, "255.255.0.0"]

Such changes will be documented