Cache tags in Laravel - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output when retrieving a tagged cache item after flushing one tag?

Consider the following Laravel cache code:

Cache::tags(['users', 'settings'])->put('config', 'value1', 3600);
Cache::tags(['users'])->flush();
$value = Cache::tags(['users', 'settings'])->get('config');
echo $value ?? 'null';

What will be printed?

Laravel

Cache::tags(['users', 'settings'])->put('config', 'value1', 3600);
Cache::tags(['users'])->flush();
$value = Cache::tags(['users', 'settings'])->get('config');
echo $value ?? 'null';

A value1

B false

C null

D Throws an exception

💡 Hint

Think about what happens when you flush a tag and how it affects cache items with multiple tags.

Flushing the 'users' tag removes all cache items tagged with 'users', including those tagged with both 'users' and 'settings'. So the item 'config' is removed and returns null.

📝 Syntax

intermediate

Which option correctly stores a value with multiple cache tags in Laravel?

Which of the following code snippets correctly stores the value 'blue' with tags 'colors' and 'themes' for 10 minutes?

A Cache::tags('colors')->tags('themes')->put('background', 'blue', 600);

B Cache::tags(['colors', 'themes'])->put('background', 'blue', 600);

C Cache::tags(['colors'], ['themes'])->put('background', 'blue', 600);

D Cache::tags('colors', 'themes')->put('background', 'blue', 600);

💡 Hint

Remember how to pass multiple tags as an array in Laravel's cache tagging.

The tags method accepts an array of tags. Chaining multiple calls or passing array of arrays is incorrect.

🔧 Debug

advanced

Why does this tagged cache retrieval return null unexpectedly?

Given this code:

Cache::tags(['session', 'user'])->put('token', 'abc123', 300);
// ... some time later
$token = Cache::tags(['user', 'session'])->get('token');
echo $token ?? 'null';

The output is 'null'. Why?

Laravel

Cache::tags(['session', 'user'])->put('token', 'abc123', 300);
$token = Cache::tags(['user', 'session'])->get('token');
echo $token ?? 'null';

A Cache tags order matters; ['user', 'session'] is different from ['session', 'user']

B The cache key 'token' was never stored

C Cache tags are case-sensitive and tags differ in case

D The cache store does not support tagging

💡 Hint

Notice that the order of the tags is reversed between put and get.

Cache tags order matters because the tags array is serialized to compute the tag root key hash. Different order produces different prefix for the item key, so retrieval fails.

❓ state_output

advanced

What is the number of items in cache after flushing one tag?

Consider these cache operations:

Cache::tags(['a', 'b'])->put('item1', 'x', 100);
Cache::tags(['a'])->put('item2', 'y', 100);
Cache::tags(['b'])->put('item3', 'z', 100);
Cache::tags(['a'])->flush();
$count = Cache::tags(['b'])->getMultiple(['item1', 'item3']);
$itemsCount = count(array_filter($count));
echo $itemsCount;

What number is printed?

Laravel

Cache::tags(['a', 'b'])->put('item1', 'x', 100);
Cache::tags(['a'])->put('item2', 'y', 100);
Cache::tags(['b'])->put('item3', 'z', 100);
Cache::tags(['a'])->flush();
$count = Cache::tags(['b'])->getMultiple(['item1', 'item3']);
$itemsCount = count(array_filter($count));
echo $itemsCount;

A 3

B 2

C 0

D 1

💡 Hint

Think about which items are removed when flushing tag 'a' and which remain under tag 'b'.

Flushing tag 'a' removes items tagged with 'a'. 'item1' has tags 'a' and 'b' so it is removed. 'item2' has 'a' only, removed. 'item3' has 'b' only, remains. So only 'item3' is returned.

🧠 Conceptual

expert

Which statement about Laravel cache tags is true?

Choose the correct statement about Laravel cache tags:

A Cache tags allow grouping cache items so flushing one tag removes only items with that tag, even if they have multiple tags.

B Cache tags require the cache key to be unique across all tags to avoid collisions.

C Cache tags can be nested to create hierarchical cache groups automatically.

D Cache tags are supported by all Laravel cache drivers including 'file' and 'database'.

💡 Hint

Think about how flushing a tag affects items with multiple tags and driver support.

Flushing a tag removes all items with that tag, even if they have other tags. Not all drivers support tags (e.g., file, database). Tags are flat, not hierarchical. Cache keys can be reused under different tags.