Custom validation rules in Laravel - Mini Project: Build & Apply

Laravel Custom Validation Rules

📖 Scenario: You are building a simple Laravel form to register users. You want to ensure the username is unique and only contains letters and numbers.

🎯 Goal: Create a custom validation rule in Laravel that checks if a username contains only letters and numbers, then apply it to a form request.

📋 What You'll Learn

Create a custom validation rule class named AlphaNumOnly

Add a passes method that returns true only if the username contains letters and numbers

Add a message method that returns a custom error message

Use the custom rule in a form request validation for the username field

💡 Why This Matters

🌍 Real World

Custom validation rules help enforce specific business logic on user input beyond built-in rules, improving data quality and user experience.

💼 Career

Laravel developers often create custom validation rules to meet unique application requirements and maintain clean, reusable validation code.

1

Create the custom validation rule class

Create a Laravel custom validation rule class named AlphaNumOnly using the artisan command php artisan make:rule AlphaNumOnly.

Laravel

# Run the artisan command to create the rule class
# Your code here

Need a hint?

Use the artisan command to create the rule class, then implement passes and message methods.

2

Add a form request class for user registration

Create a Laravel form request class named RegisterUserRequest using the artisan command php artisan make:request RegisterUserRequest.

Laravel

<?php

namespace App\Rules;

use Illuminate\Contracts\Validation\Rule;

class AlphaNumOnly implements Rule
{
    public function passes($attribute, $value)
    {
        return preg_match('/^[a-zA-Z0-9]+$/', $value) === 1;
    }

    public function message()
    {
        return 'The :attribute may only contain letters and numbers.';
    }
}

// Create the RegisterUserRequest class using artisan
# Your code here

Need a hint?

Use the artisan command to create the form request class.

3

Add validation rules to the form request

In the RegisterUserRequest class, add a rules method that returns an array with the username field using the required, unique:users,username, and the custom AlphaNumOnly rule.

Laravel

<?php

namespace App\Rules;

use Illuminate\Contracts\Validation\Rule;

class AlphaNumOnly implements Rule
{
    public function passes($attribute, $value)
    {
        return preg_match('/^[a-zA-Z0-9]+$/', $value) === 1;
    }

    public function message()
    {
        return 'The :attribute may only contain letters and numbers.';
    }
}

// Command run in terminal:
// php artisan make:request RegisterUserRequest

namespace App\Http\Requests;

use Illuminate\Foundation\Http\FormRequest;
use App\Rules\AlphaNumOnly;

class RegisterUserRequest extends FormRequest
{
    public function authorize()
    {
        return true;
    }

    public function rules()
    {
        // Add validation rules here
        # Your code here
    }
}

Need a hint?

Return an array with the username key and the required validation rules including the custom rule.

4

Use the form request in the controller

In your UserController, update the store method to accept the RegisterUserRequest as a parameter and use it to validate the incoming request.

Laravel

 ['required', 'unique:users,username', new AlphaNumOnly()],
        ];
    }
}

namespace App\Http\Controllers;

use App\Http\Requests\RegisterUserRequest;

class UserController extends Controller
{
    public function store(RegisterUserRequest $request)
    {
        // Add code to create user with validated data
        # Your code here
    }
}

Need a hint?

Use the form request as a parameter and call User::create with the validated data.