Note
This library is in active development. The API may change in future versions as we refine and improve the developer experience based on real-world usage and feedback.
Lemmon Validator is a comprehensive, fluent validation and data processing library for PHP that prioritizes developer experience, type safety, and real-world practicality. Inspired by modern validation libraries like Valibot and Zod, it brings a chainable, readable API to PHP for validation, transformation, and sanitization with intelligent error handling and form-safe defaults.
composer require lemmon/validatorRequirements: PHP 8.1 or higher
Philosophy: "Simple and Minimal with Extensibility Over Reinvention"
Rather than reimplementing every possible transformation or validation rule, Lemmon Validator provides a solid foundation with generic transform() and pipe() methods that integrate seamlessly with PHP's ecosystem. Need complex string transformations? Plug in Laravel's Str class through our transformation system. Need advanced array operations? Connect Laravel Collections via our fluent API. The library focuses on what it does best: type-safe validation with excellent developer experience, while enabling you to leverage the entire PHP ecosystem.
Key Design Principles:
- Form Safety First: Empty strings coerce to
null(not dangerous0/false) to prevent real-world issues like accidental zero bank balances - Fluent API: Validation rules read like natural language -
Validator::isString()->email()->required() - Comprehensive Error Collection: All validation errors are collected, not just the first failure
- Type-Aware Transformations: Intelligent transformation system that maintains type context and handles coercion automatically
- Extensible Architecture: Generic transformation methods work with any PHP callable or external library
- Type-safe validation for strings, integers, floats, arrays, and objects
- Fluent, chainable API for readable and maintainable validation rules
- Comprehensive error collection with detailed, structured feedback
- Intuitive custom validation with
satisfies()method and optional error messages - Logical combinators (
Validator::allOf(),Validator::anyOf(),Validator::not()) for complex validation logic - Form-safe coercion - empty strings become
null(not dangerous0/false) for real-world safety - Schema validation for nested data structures
- Universal transformations (
transform(),pipe()) for post-validation data processing - Null-safe operations with
nullifyEmpty()method for consistent empty value handling
use Lemmon\Validator;
// Simple validation with form-safe coercion
$email = Validator::isString()
->email()
->nullifyEmpty() // Empty strings become null (form-safe)
->validate('[email protected]');
// Schema validation with custom logic
$userSchema = Validator::isAssociative([
'name' => Validator::isString()->required(),
'age' => Validator::isInt()->min(18)->coerce(),
'email' => Validator::isString()->email()->nullifyEmpty(),
'password' => Validator::isString()->satisfies(fn($v) => strlen($v) >= 8, 'Password too short')
]);
// Tuple-based validation (no exceptions)
[$valid, $user, $errors] = $userSchema->tryValidate($input);
// Exception-based validation
$user = $userSchema->validate($input); // Throws ValidationException on failure- String Validation - Email, URL, patterns, length constraints
- Numeric Validation - Integers, floats, ranges, constraints
- Array Validation - Indexed arrays and item validation
- Object & Schema Validation - Complex nested structures
- Custom Validation - User-defined functions and business logic
- Error Handling - Working with validation errors
We welcome contributions! Please see our Contributing Guide for details.
This project is licensed under the MIT License - see the LICENSE file for details.