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#Types

Flow Types is a small library that provides a set of type classes for PHP. It's designed to work together with static analysis tools like PHPStan and Psalm.

The main goal of this library is to simplify common type-related tasks, such as type checking, type casting, and type assertion.

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#Installation

composer require flow-php/types:~0.16.2

#Usage

#Type Narrowing

To narrow a variable to a specific type, you can use one of two available methods:

• Type::isValid(mixed $value) : bool
• Type::assert(mixed $value) : mixed

The main difference between those two, is that isValid returns a boolean value, while assert will throw an exception if the type is not valid.

Examples:

<?php

use Flow\Types\DSL\type_string;

$variable = $input->get('some-input');

$string = type_string()->assert($variable); 

The above code will throw an exception if the variable is not a string. On top of that it will also narrow the $string variable to a string type, so you can use it without any additional checks.

<?php

use Flow\Types\DSL\type_string;

$variable = $input->get('some-input');

function doSomething(string $string): void
{
    // do something with string
}

if (type_string()->isValid($variable)) {
    doSomething($variable);
} 

The above code will check if the variable is a string, and if it is, it will call the doSomething function with the variable. Thanks to the isValid method, you can use the variable without any additional checks and static analysis tools will not complain about it.

#Type Casting

To cast a variable to a specific type, you just simply need to use the cast method:

Note: The cast method will throw CastingException if the variable cannot be casted to the specified type.

When passed value already has a valid type it's returned as is.

<?php

use Flow\Types\DSL\type_string;

$variable = $input->get('some-input');

$string = type_string()->cast($variable); 

#Complex Types

By default all types are not nullabe, in order to achieve nullability two types needs to be combined:

• type_optional(type_string()) - results in nullable string '?string'
• type_union(type_string(),type_integer(),type_null()) - results in union<string,integer,null> which is the same as string|integer|null

#Lists

List is a collection of elements of the same where keys start from 0 and are auto incremented.

<?php

use Flow\Types\DSL\type_list;
use Flow\Types\DSL\type_string;

$listOfStrings = type_list(type_string());

#Maps

Map is a key value data structure where all keys and all values has the same type.

<?php

use Flow\Types\DSL\type_map;
use Flow\Types\DSL\type_string;
use Flow\Types\DSL\type_integer;

$mapOfStringToInt = type_map(type_string(), type_integer());

#Structures

Structure is a associative array with a defined shape.

<?php

use Flow\Types\DSL\type_structure;
use Flow\Types\DSL\type_string;
use Flow\Types\DSL\type_integer;

$userStructure = type_structure([
    'id' => type_string(),
    'name' => type_string()
])

#Combined Types

All above types can be easily combined together, so for to get the list of users:

<?php

use Flow\Types\DSL\type_list;
use Flow\Types\DSL\type_structure;
use Flow\Types\DSL\type_string;
use Flow\Types\DSL\type_integer;

$userStructure = type_list(
    type_structure([
        'id' => type_string(),
        'name' => type_string()
    ])
);