Request validation basics in Laravel

Introduction

Request validation helps check user input before saving or using it. It stops wrong or harmful data early.

When a user submits a form with data like name or email.

When an API receives data from another app or service.

When you want to make sure required fields are filled.

When you want to limit input length or format (like a phone number).

When you want to give clear error messages if input is wrong.

Syntax

Laravel

public function store(Request $request)
{
    $validated = $request->validate([
        'field_name' => 'required|string|max:255',
        'email' => 'required|email',
    ]);

    // Use $validated data
}

The validate method checks the rules and stops if input is invalid.

Rules are written as strings separated by pipes |.

Examples

This checks that username is required, only letters and numbers, and length between 3 and 20.

Laravel

$request->validate([
    'username' => 'required|alpha_num|min:3|max:20',
]);

This allows age to be empty or an integer 18 or older.

Laravel

$request->validate([
    'age' => 'nullable|integer|min:18',
]);

This checks email is required, valid format, and unique in users table.

Laravel

$request->validate([
    'email' => 'required|email|unique:users,email',
]);

Sample Program

This controller method checks the input for name, email, and password. It stops if any rule fails. If all pass, it returns a success message with the validated data.

Laravel

<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;

class UserController extends Controller
{
    public function store(Request $request)
    {
        $validated = $request->validate([
            'name' => 'required|string|max:50',
            'email' => 'required|email|unique:users,email',
            'password' => 'required|string|min:6',
        ]);

        // Imagine saving user here

        return response()->json([
            'message' => 'User created successfully!',
            'data' => $validated
        ]);
    }
}

Important Notes

Validation errors automatically redirect back with messages in web apps.

You can customize error messages by passing a second array to validate.

Use Laravel's built-in rules to cover many common cases easily.

Summary

Request validation checks user input early to keep data safe and correct.

Use the validate method with rules to define what input is allowed.

Validation stops the request if input is wrong and shows helpful errors.

Practice

1. What is the main purpose of request validation in Laravel?

easy

A. To check user input early and ensure data is safe and correct

B. To speed up the server response time

C. To format the output HTML automatically

D. To connect to the database securely

Solution

1. Step 1: Understand request validation role

   Request validation checks user input before processing to avoid bad data.

2. Step 2: Identify main goal

   The main goal is to keep data safe and correct by stopping invalid input early.

3. Final Answer:

   To check user input early and ensure data is safe and correct -> Option A

4. Quick Check:

   Request validation = safe, correct input [OK]

Hint: Validation protects data by checking input early [OK]

Common Mistakes:

• Thinking validation speeds up server
• Confusing validation with output formatting
• Assuming validation manages database connections

2. Which of the following is the correct syntax to validate a request field named email as required and must be a valid email in a Laravel controller?

easy

A. $request->validate(['email' => 'required|email']);

B. $request->validate(['email' => 'email||required']);

C. $request->validate(['email' => 'required,email']);

D. $request->validate(['email' => ['required', email]]);

Solution

1. Step 1: Recall Laravel validation syntax

   Laravel uses pipe-separated strings for rules like 'required|email'.

2. Step 2: Check each option

   $request->validate(['email' => ['required', email]]);: syntax error ('email' not quoted in array). $request->validate(['email' => 'email||required']);: 'email||required' has empty invalid rule. $request->validate(['email' => 'required,email']);: uses comma which is invalid. $request->validate(['email' => 'required|email']);: correct pipe syntax.

3. Final Answer:

   $request->validate(['email' => 'required|email']); -> Option A

4. Quick Check:

   Pipe-separated rules = correct syntax [OK]

Hint: Use pipes '|' to separate validation rules in strings [OK]

Common Mistakes:

• Using commas instead of pipes
• Syntax errors in array rule lists
• Double pipes creating empty rules

3. Given this Laravel controller code snippet:

public function store(Request $request) {
    $validated = $request->validate([
        'age' => 'required|integer|min:18'
    ]);
    return $validated['age'];
}

What will be the output if the request sends age=20?

medium

A. Validation error: age is required

B. Validation error: age must be at least 18

C. null

D. 20

Solution

1. Step 1: Understand validation rules

   Field 'age' must be present, an integer, and minimum 18.

2. Step 2: Check input value

   Input age=20 meets all rules: present, integer, and >=18.

3. Step 3: Determine output

   Validation passes, so $validated['age'] returns 20.

4. Final Answer:

   20 -> Option D

5. Quick Check:

   Valid input returns value [OK]

Hint: Valid input passes and returns validated data [OK]

Common Mistakes:

• Assuming validation error for valid input
• Confusing min rule with max
• Expecting null when validation passes

4. Identify the error in this Laravel validation code:

public function update(Request $request) {
    $request->validate([
        'username' => 'required|min:5|max'
    ]);
}

medium

A. The 'required' rule cannot be combined with 'min'

B. The 'max' rule is missing a value, causing a syntax error

C. The 'min' rule should be 'min=5' instead of 'min:5'

D. The validate method should be called on the controller, not the request

Solution

1. Step 1: Review validation rules syntax

   Rules like 'min' and 'max' require a value after colon, e.g., 'max:10'.

2. Step 2: Identify error in code

   The 'max' rule is written without a value, which is invalid syntax.

3. Final Answer:

   The 'max' rule is missing a value, causing a syntax error -> Option B

4. Quick Check:

   Rules need values after colon [OK]

Hint: Always provide values for min/max rules after colon [OK]

Common Mistakes:

• Omitting values for min/max rules
• Using '=' instead of ':' in rules
• Calling validate on wrong object

5. You want to validate a request in Laravel where the password field is required, must be at least 8 characters, and must be confirmed by a matching password_confirmation field. Which validation rule set correctly enforces this?

hard

A. ['password' => 'required|confirmed', 'password_confirmation' => 'min:8']

B. ['password' => 'required|min:8', 'password_confirmation' => 'required']

C. ['password' => 'required|min:8|confirmed']

D. ['password' => 'required|min:8', 'password_confirmation' => 'same,password']

Solution

1. Step 1: Understand Laravel's confirmed rule

   The 'confirmed' rule checks if a matching field with '_confirmation' suffix exists and matches.

2. Step 2: Check each option

   ['password' => 'required|min:8|confirmed'] uses 'confirmed' with 'min:8' and 'required' on password only, which is correct. ['password' => 'required|min:8', 'password_confirmation' => 'required'] requires password_confirmation but does not check matching. ['password' => 'required|confirmed', 'password_confirmation' => 'min:8'] misplaces min:8 on confirmation. ['password' => 'required|min:8', 'password_confirmation' => 'same,password'] uses invalid 'password' rule.

3. Final Answer:

   ['password' => 'required|min:8|confirmed'] -> Option C

4. Quick Check:

   Use 'confirmed' rule for password confirmation [OK]

Hint: Use 'confirmed' rule to check matching confirmation field [OK]

Common Mistakes:

• Forgetting to add 'confirmed' rule
• Validating confirmation field separately
• Using 'same' instead of 'confirmed' rule