Custom validation rules in Laravel - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this custom validation rule in Laravel?

Consider this Laravel custom validation rule class that checks if a string contains only vowels. What will be the validation result for the input 'aeiou'?

Laravel

namespace App\Rules;

use Illuminate\Contracts\Validation\Rule;

class OnlyVowels implements Rule
{
    public function passes($attribute, $value)
    {
        return preg_match('/^[aeiou]+$/i', $value) === 1;
    }

    public function message()
    {
        return 'The :attribute must contain only vowels.';
    }
}

// Usage in a controller validation:
$request->validate([
    'word' => ['required', new OnlyVowels],
]);

A The validation fails because the regex is incorrect and matches consonants.

B The validation fails because 'aeiou' contains uppercase letters.

C The validation passes because 'aeiou' contains only vowels.

D The validation passes only if the input is exactly 'aeiou'.

💡 Hint

Look at the regex pattern and the preg_match flags.

The regex '/^[aeiou]+$/i' matches strings that contain only vowels, case-insensitive. 'aeiou' matches this pattern, so the validation passes.

📝 Syntax

intermediate

Which option correctly defines a Laravel custom validation rule class?

Identify the option that correctly implements a Laravel custom validation rule class named 'Uppercase' that checks if a string is all uppercase.

A

class Uppercase implements Rule {
    public function passes($attribute, $value) {
        return strtoupper($value) === $value;
    }
    public function message() {
        return 'The :attribute must be uppercase.';
    }
}

B

class Uppercase extends Rule {
    public function passes($value) {
        return strtoupper($value) === $value;
    }
    public function message() {
        return 'The :attribute must be uppercase.';
    }
}

C

class Uppercase implements Rule {
    public function passes($attribute, $value) {
        return strtoupper($value) == $value;
    }
    public function message() {
        return 'The :attribute must be uppercase.';
    }
}

D

class Uppercase implements Rule {
    public function passes($attribute, $value) {
        return strtoupper($value) === $value
    }
    public function message() {
        return 'The :attribute must be uppercase.';
    }
}

💡 Hint

Check method signatures and syntax correctness.

Option A correctly implements the Rule interface with the required passes method signature and uses strict equality. Option A incorrectly extends Rule (should implement), C uses loose equality (==), and D misses a semicolon causing syntax error.

🔧 Debug

advanced

Why does this Laravel custom validation rule always fail?

Given this custom rule code, why does validation always fail regardless of input? class NumericString implements Rule { public function passes($attribute, $value) { return is_numeric($value) && is_string($value); } public function message() { return 'The :attribute must be a numeric string.'; } }

A Because the message method should return a boolean, not a string.

B Because the class does not implement the Rule interface.

C Because the passes method is missing the $attribute parameter.

D Because is_numeric returns true for numbers but is_string returns false for numeric values, so the condition is never true.

💡 Hint

Think about what is_numeric and is_string check for.

is_numeric returns true for numeric strings and numbers, but is_string returns true only for strings. If $value is a number type, is_string returns false, so the combined condition fails. This causes the rule to fail for numeric strings that are not strings.

❓ state_output

advanced

What is the validation error message output for this custom rule?

If a Laravel custom validation rule class returns this message method: public function message() { return 'The :attribute must be a palindrome.'; } And the attribute name is 'username', what is the final error message shown to the user?

A username must be a palindrome.

B The username must be a palindrome.

C The :attribute must be a palindrome.

D The username must be a palindrome

💡 Hint

Laravel replaces :attribute with the field name in error messages.

Laravel automatically replaces the placeholder :attribute with the actual field name, so the message becomes 'The username must be a palindrome.'

🧠 Conceptual

expert

Which statement about Laravel custom validation rules is TRUE?

Select the correct statement about Laravel custom validation rules.

A Custom validation rules can be implemented as invokable classes or using the Rule interface.

B Custom validation rules must always extend the base Validator class to work.

C Custom validation rules cannot access other request data during validation.

D Custom validation rules must return a boolean from the message() method.

💡 Hint

Think about how Laravel allows custom rules to be created.

Laravel allows custom validation rules to be created either by implementing the Rule interface or by creating invokable classes. They do not need to extend Validator. The message() method returns a string, not boolean. Custom rules can access other data if passed properly.

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