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.