Request validation basics in Laravel - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of request validation in Laravel?

Request validation ensures that the data sent by users meets the rules your application expects before processing it. It helps keep your app safe and reliable.

beginner

How do you validate a request in a Laravel controller using the validate method?

You call $request->validate([ 'field' => 'rules' ]) inside your controller method. Laravel checks the data and automatically redirects back with errors if validation fails.

beginner

What happens if validation fails when using $request->validate()?

Laravel automatically redirects the user back to the previous page with error messages and old input data, so the user can fix mistakes easily.

beginner

Name two common validation rules in Laravel and what they check.

required: Ensures the field is present and not empty.
email: Checks if the field contains a valid email address.

intermediate

How can you customize the error messages shown after validation fails?

You can pass a second argument to <code>validate()</code> with an array of custom messages, or define messages in a Form Request class for cleaner code.

Which Laravel method is commonly used to validate incoming request data inside a controller?

A $request->validate()

B validateRequest()

C checkValidation()

D validateInput()

The correct method is $request->validate(), which applies validation rules to the incoming data.

What does the 'required' validation rule check for?

A Field must be a number

B Field must be unique

C Field must be a valid email

D Field must be present and not empty

The 'required' rule ensures the field is present in the request and is not empty.

If validation fails, what does Laravel do by default?

A Redirects back with error messages

B Sends a success response

C Continues processing without errors

D Deletes the request data

Laravel redirects the user back to the previous page with error messages and old input.

Where can you define validation rules besides directly in the controller?

A In the database migration

B In the routes file

C In a Form Request class

D In the .env file

Form Request classes are dedicated classes to organize validation logic cleanly.

How do you provide custom error messages for validation rules?

A By editing the Laravel core files

B By passing a second argument to $request->validate() with messages

C By changing the database schema

D By modifying the routes file

You can pass an array of custom messages as the second argument to $request->validate().

Explain how Laravel handles request validation inside a controller using the validate method.

Think about what happens when data does not meet the rules.

Describe two common validation rules in Laravel and what they check for.

Focus on simple, frequently used rules.

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