Storing and retrieving cache in Laravel - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this Laravel cache retrieval code?

Consider this Laravel code snippet that stores and retrieves a cache value. What will be the output when the code runs?

Laravel

<?php
use Illuminate\Support\Facades\Cache;

Cache::put('user_count', 15, 10);
$value = Cache::get('user_count');
echo $value;

A 15

B null

C Throws an exception

D 0

💡 Hint

Think about what Cache::put and Cache::get do in Laravel.

The code stores the value 15 in the cache with the key 'user_count' for 10 seconds. Then it retrieves the value using Cache::get. Since the key exists, it returns 15.

📝 Syntax

intermediate

Which option correctly stores a value in Laravel cache for 5 minutes?

You want to store the string 'hello' in the cache with the key 'greeting' for 5 minutes. Which code snippet is correct?

A Cache::put('greeting', 'hello', 5);

B Cache::put('greeting', 'hello', now()->addMinutes(5));

C Cache::put('greeting', 'hello', 5 * 60);

D Cache::put('greeting', 'hello', '5 minutes');

💡 Hint

Laravel cache expiration can be a DateTime or a number of seconds.

Options B and C are correct. B uses a DateTime instance (now()->addMinutes(5)). C uses 300 seconds (5 * 60 = 5 minutes). Option A uses 5 seconds (too short). Option D uses invalid string syntax.

🔧 Debug

advanced

Why does this Laravel cache retrieval return null?

Given this code, why does Cache::get('session_data') return null?

Laravel

<?php
use Illuminate\Support\Facades\Cache;

Cache::put('session_data', ['id' => 1, 'name' => 'Alice'], 1);
$value = Cache::get('session_data');
// After 2 minutes
$valueAfter = Cache::get('session_data');

A The cache driver does not support storing arrays.

B The cache key was never set, so it returns null.

C The cache expired after 1 second, so after 2 minutes the value is null.

D Cache::get always returns null for arrays.

💡 Hint

Think about the expiration time and when the retrieval happens.

The cache was set to expire after 1 second. Retrieving after 2 minutes means the cache expired and returns null.

🧠 Conceptual

advanced

What happens if you use Cache::remember with a closure in Laravel?

What is the behavior of Cache::remember('key', 10, fn() => expensiveFunction()) in Laravel?

A It always runs expensiveFunction() and ignores the cache.

B It returns the cached value if it exists; otherwise, it runs expensiveFunction(), caches the result for 10 minutes, and returns it.

C It caches the closure itself instead of the result.

D It throws an error because closures cannot be cached.

💡 Hint

Cache::remember is designed to cache the result of the closure.

Cache::remember checks if the key exists. If yes, returns cached value. If no, runs the closure, caches its return value, then returns it.

❓ state_output

expert

What is the output of this Laravel cache increment code?

Given this code, what is the final value of $count after execution?

Laravel

<?php
use Illuminate\Support\Facades\Cache;

Cache::put('count', 5, 10);
Cache::increment('count');
Cache::increment('count', 3);
$count = Cache::get('count');
echo $count;

A Throws an error because increment requires an integer

B 8

C 5

D 9

💡 Hint

Increment adds to the cached value each time.

Initial value is 5. First increment adds 1 (default), second adds 3, total 5 + 1 + 3 = 9.

Practice

1. What does the Cache::put('key', 'value', 60) method do in Laravel?

easy

A. Stores 'value' permanently in cache without expiration

B. Retrieves 'value' from cache with 'key' and expires in 60 seconds

C. Deletes the cache entry with 'key' after 60 minutes

D. Stores 'value' in cache under 'key' for 60 minutes

Solution

1. Step 1: Understand Cache::put method

   The Cache::put method stores data in the cache with a key and expiration time in minutes.

2. Step 2: Analyze the parameters

   Here, 'key' is the cache key, 'value' is the data stored, and 60 means it expires after 60 minutes.

3. Final Answer:

   Stores 'value' in cache under 'key' for 60 minutes -> Option D

4. Quick Check:

   Cache::put stores with expiration = A [OK]

Hint: Cache::put stores with minutes expiry, not seconds [OK]

Common Mistakes:

• Confusing expiration time units (seconds vs minutes)
• Thinking Cache::put retrieves data
• Assuming Cache::put stores data permanently

2. Which of the following is the correct syntax to retrieve a cached value with a default fallback in Laravel?

easy

A. Cache::get('key', 'default')

B. Cache::retrieve('key', 'default')

C. Cache::fetch('key', 'default')

D. Cache::find('key', 'default')

Solution

1. Step 1: Identify Laravel cache retrieval method

   Laravel uses Cache::get to retrieve cached data safely.

2. Step 2: Check method parameters

   The second parameter is the default value returned if the key is not found.

3. Final Answer:

   Cache::get('key', 'default') -> Option A

4. Quick Check:

   Cache::get with default = A [OK]

Hint: Use Cache::get to retrieve with default fallback [OK]

Common Mistakes:

• Using non-existent methods like retrieve or fetch
• Forgetting the default fallback parameter
• Using Cache::put instead of Cache::get

3. What will be the output of this Laravel code snippet?

Cache::put('count', 5, 10);
$value = Cache::get('count', 0);
echo $value;

medium

A. 0

B. null

C. 5

D. Error

Solution

1. Step 1: Store value in cache

   The code stores the integer 5 under the key 'count' with expiration 10 minutes.

2. Step 2: Retrieve value from cache

   Then it retrieves 'count' with default 0. Since the key exists, it returns 5.

3. Final Answer:

   5 -> Option C

4. Quick Check:

   Cache::get returns stored value if exists = B [OK]

Hint: Cache::get returns stored value, not default if key exists [OK]

Common Mistakes:

• Assuming default value is always returned
• Confusing expiration time with immediate deletion
• Expecting null or error instead of stored value

4. Identify the error in this Laravel cache usage:

Cache::put('user', 'Alice');
$value = Cache::get('user');
echo $value;

medium

A. Cache::put requires expiration time as third argument

B. Cache::get requires a default value parameter

C. Cache::put key must be numeric

D. Cache::get cannot be used without Cache::forever

Solution

1. Step 1: Check Cache::put usage

   Cache::put requires three parameters: key, value, and expiration time in minutes.

2. Step 2: Identify missing expiration

   The code misses the expiration time, so it will cause an error or unexpected behavior.

3. Final Answer:

   Cache::put requires expiration time as third argument -> Option A

4. Quick Check:

   Cache::put needs expiration time = D [OK]

Hint: Always provide expiration time with Cache::put unless using forever [OK]

Common Mistakes:

• Omitting expiration time in Cache::put
• Thinking Cache::get always needs default
• Believing keys must be numeric

5. You want to store a user's settings permanently in cache and then remove them later. Which sequence of Laravel cache methods is correct?

hard

A. Cache::store('settings', $data); Cache::remove('settings');

B. Cache::forever('settings', $data); Cache::forget('settings');

C. Cache::put('settings', $data, 0); Cache::delete('settings');

D. Cache::save('settings', $data); Cache::clear('settings');

Solution

1. Step 1: Store data permanently

   Use Cache::forever to store data without expiration.

2. Step 2: Remove cached data

   Use Cache::forget to delete the cached key when needed.

3. Final Answer:

   Cache::forever('settings', $data); Cache::forget('settings'); -> Option B

4. Quick Check:

   Permanent store + forget = C [OK]

Hint: Use forever to store permanently, forget to delete [OK]

Common Mistakes:

• Using wrong method names like delete or remove
• Passing 0 as expiration to put for permanent storage
• Confusing Cache::store or Cache::save as valid methods