README

PHP string utilities providing both mutable and immutable string objects with UTF-8 safe helpers.

This library offers two complementary string abstractions:

StrImmutable — an immutable string value object
Str — a mutable string helper with fluent API

Both share the same transformation methods and behavior.

Requirements

PHP 8.1 or higher
ext-iconv

Installation

composer require guillaumetissier/string

Which class should I use?

StrImmutable (recommended)

Use StrImmutable when you want:

predictability
value object semantics
no side effects

use Guillaumetissier\String\StrImmutable;

$original = StrImmutable::of('Hello World');

$slug = $original->slug();

echo $original; // Hello World
echo $slug;     // hello-world

Each method returns a new instance.

Str (mutable)

Use Str when you want:

in-place transformations
fluent chaining without creating new objects
scripting or performance-oriented usage

use Guillaumetissier\String\Str;

$str = Str::of('Hello World')->lower()->replace(' ', '-');

echo $str; // hello-world

All methods modify the internal value and return $this.

Common API

Both classes expose the same public methods.

Creation & access

::of(string $value)
->value(): string
(string) $str

Length & state

->length(): int          // UTF-8 safe
->isEmpty(): bool
->isNotEmpty(): bool

Case & trimming

->trim()
->lower()
->upper()
->lowerFirst()
->upperFirst()
->snake()   // snake_case
->camel()   // camelCase
->kebab()   // kebab-case

Search

->startsWith(string $needle): bool
->endsWith(string $needle): bool
->contains(string $needle): bool

Replace

->replace(string $search, string $replace)

Substrings

->substr(int $start, ?int $length = null)

Padding

->pad(int $length, string $pad = ' ', int $type = STR_PAD_RIGHT)

Supports STR_PAD_LEFT, STR_PAD_RIGHT, STR_PAD_BOTH.

Slug

->slug(string $separator = '-')

Creates a URL-friendly ASCII slug.

Comparison

->equals(string|StrInterface $other): bool

JSON serialization

Both classes implement JsonSerializable.

json_encode(StrImmutable::of('test')); // "test"
json_encode(Str::of('test'));          // "test"

Design principles

No global helper functions
UTF-8 safe where applicable
No framework dependency
Explicit mutability
Small, focused API

guillaumetissier / string

Maintainers

Details