Custom validation rules in Laravel

Introduction

Custom validation rules let you check data in your own way when the built-in checks are not enough.

You want to check if a username is unique in a special way.

You need to validate a password with custom strength rules.

You want to verify a code format that Laravel does not support by default.

You want to reuse a complex validation logic in many places.

You want to keep your validation clean and organized.

Syntax

Laravel

php artisan make:rule RuleName

// Then in app/Rules/RuleName.php

namespace App\Rules;

use Illuminate\Contracts\Validation\Rule;

class RuleName implements Rule
{
    public function passes($attribute, $value)
    {
        // return true if valid, false if not
    }

    public function message()
    {
        return 'The validation error message.';
    }
}

The passes method checks if the value is valid.

The message method returns the error message shown if validation fails.

Examples

This rule checks if the input is all uppercase letters.

Laravel

<?php

namespace App\Rules;

use Illuminate\Contracts\Validation\Rule;

class Uppercase implements Rule
{
    public function passes($attribute, $value)
    {
        return strtoupper($value) === $value;
    }

    public function message()
    {
        return 'The :attribute must be uppercase.';
    }
}

Apply the custom rule by creating a new instance inside the validation array.

Laravel

// Using the rule in a controller
$request->validate([
    'name' => ['required', new Uppercase()],
]);

Sample Program

This example creates a rule to check if a number is even. The controller uses it to validate input.

Laravel

<?php

namespace App\Rules;

use Illuminate\Contracts\Validation\Rule;

class EvenNumber implements Rule
{
    public function passes($attribute, $value)
    {
        return is_numeric($value) && $value % 2 === 0;
    }

    public function message()
    {
        return 'The :attribute must be an even number.';
    }
}

// In a controller method
public function store(Request $request)
{
    $request->validate([
        'number' => ['required', new EvenNumber()],
    ]);

    return 'Number is valid and even!';
}

Important Notes

You can pass extra data to your rule by adding a constructor.

Custom rules help keep validation logic reusable and clean.

Summary

Custom validation rules let you create your own checks for data.

They have two main methods: passes and message.

Use them in validation arrays by creating new instances.

Practice

1. What is the main purpose of creating a custom validation rule in Laravel?

easy

A. To define your own logic for validating data beyond built-in rules

B. To change the database schema automatically

C. To create new database tables

D. To generate HTML forms automatically

Solution

1. Step 1: Understand Laravel validation rules

   Laravel provides built-in rules but sometimes you need to check data in a way not covered by them.

2. Step 2: Purpose of custom validation rules

   Custom rules let you write your own logic to validate data exactly as you want.

3. Final Answer:

   To define your own logic for validating data beyond built-in rules -> Option A

4. Quick Check:

   Custom validation = custom logic [OK]

Hint: Custom rules check data your way, not Laravel's default [OK]

Common Mistakes:

• Thinking custom rules change database structure
• Confusing validation with form generation
• Assuming custom rules create tables

2. Which method must you implement in a Laravel custom validation rule class to check if the data passes validation?

easy

A. check

B. message

C. validate

D. passes

Solution

1. Step 1: Recall custom rule methods

   Laravel custom validation rules require two methods: passes and message.

2. Step 2: Identify method for validation logic

   The passes method contains the logic to decide if the data is valid or not.

3. Final Answer:

   passes -> Option D

4. Quick Check:

   passes() checks data validity [OK]

Hint: passes() returns true/false for validation [OK]

Common Mistakes:

• Using message() to check data validity
• Assuming validate() or check() are required methods
• Confusing method names

3. Given this custom rule class snippet, what will $rule->passes('age', 17) return?

class AdultRule implements \Illuminate\Contracts\Validation\Rule {
    public function passes($attribute, $value) {
        return $value >= 18;
    }
    public function message() {
        return 'You must be an adult.';
    }
}

medium

A. true

B. Throws an error

C. false

D. null

Solution

1. Step 1: Understand the passes method logic

   The method returns true if the value is 18 or more, false otherwise.

2. Step 2: Evaluate passes with value 17

   Since 17 is less than 18, the method returns false.

3. Final Answer:

   false -> Option C

4. Quick Check:

   17 < 18 means passes() = false [OK]

Hint: Check condition in passes() with given value [OK]

Common Mistakes:

• Assuming 17 passes as adult
• Thinking passes() throws error for numbers
• Confusing message() with passes()

4. What is wrong with this custom validation rule class?

class EvenNumberRule implements \Illuminate\Contracts\Validation\Rule {
    public function passes($attribute, $value) {
        return $value % 2 == 0
    }
    public function message() {
        return 'The number must be even.';
    }
}

medium

A. message method should return a boolean

B. Missing semicolon after return statement in passes method

C. passes method should accept only one parameter

D. Class must extend a base validation class

Solution

1. Step 1: Check syntax in passes method

   The return statement lacks a semicolon at the end, causing a syntax error.

2. Step 2: Verify other method signatures

   message() correctly returns a string, passes() correctly has two parameters, and implementing the interface is enough.

3. Final Answer:

   Missing semicolon after return statement in passes method -> Option B

4. Quick Check:

   Missing semicolon = syntax error [OK]

Hint: Look for missing semicolons in PHP code [OK]

Common Mistakes:

• Thinking message() must return boolean
• Assuming passes() takes one parameter
• Believing class must extend base class

5. You want to create a custom validation rule that checks if a string contains only vowels. Which approach correctly implements the passes method?

hard

A. return preg_match('/^[aeiouAEIOU]+$/', $value) === 1;

B. return strlen($value) > 0 && ctype_alpha($value);

C. return strpos($value, 'aeiou') !== false;

D. return $value == strtolower($value);

Solution

1. Step 1: Understand the requirement

   The string must contain only vowels (a, e, i, o, u) in any case.

2. Step 2: Analyze each option

   return preg_match('/^[aeiouAEIOU]+$/', $value) === 1; uses regex to check if the string contains only vowels from start to end. return strlen($value) > 0 && ctype_alpha($value); checks only letters but not vowels. return strpos($value, 'aeiou') !== false; checks if 'aeiou' substring exists, which is incorrect. return $value == strtolower($value); checks if string is lowercase, unrelated to vowels.

3. Final Answer:

   return preg_match('/^[aeiouAEIOU]+$/', $value) === 1; -> Option A

4. Quick Check:

   Regex matching only vowels = correct passes() [OK]

Hint: Use regex to match only vowels in string [OK]

Common Mistakes:

• Using ctype_alpha without vowel check
• Checking substring instead of full string
• Confusing case check with vowel check