Cache tags in Laravel - Step-by-Step Execution

Concept Flow - Cache tags

Store item with tags

↓

Cache saves item under tags

↓

Retrieve item by tags

↓

Check if item exists

Yes No↓

Return item

↓

Flush all items with tag

↓

Tagged items removed

Cache tags let you group cached items by labels. You can store, retrieve, or clear all items with the same tag easily.

Execution Sample

Laravel

Cache::tags(['users', 'settings'])->put('user_1', 'John', 3600);
$value = Cache::tags(['users'])->get('user_1');
Cache::tags(['users'])->flush();

Stores 'John' under 'user_1' with tags 'users' and 'settings', retrieves it by 'users' tag, then clears all 'users' tagged cache.

Execution Table

Step	Action	Tags Used	Key	Value	Cache State
1	Put item	['users', 'settings']	user_1	'John'	{user_1: 'John' tagged with users, settings}
2	Get item	['users']	user_1	'John'	{user_1: 'John' tagged with users, settings}
3	Flush tag	['users']	-	-	{}
4	Get item after flush	['users']	user_1	null	{}

💡 Cache is empty after flushing 'users' tag, so retrieval returns null.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4
Cache contents	{}	{user_1: 'John' tagged with users, settings}	{user_1: 'John' tagged with users, settings}	{}	{}
Retrieved value	null	'John'	'John'	null	null

Key Moments - 2 Insights

Why does flushing the 'users' tag remove the cached item even though it also has the 'settings' tag?

Because cache tags group items, flushing any tag removes all items tagged with it regardless of other tags. See step 3 in execution_table where flushing 'users' clears the item.

What happens if you try to get a cached item with a tag that was not used when storing it?

The item won't be found because tags filter cache keys. You must use at least one tag that matches the stored tags. Step 2 shows retrieval with 'users' tag works because it matches stored tags.

Visual Quiz - 3 Questions

Look at the execution table, what is the cache state after step 1?

A {}

B {user_1: 'John' tagged with users, settings}

C {user_1: 'John' tagged with users}

D null

💡 Hint

Check the 'Cache State' column in row for step 1.

At which step does the cache become empty?

A Step 2

B Step 4

C Step 3

D Never

💡 Hint

Look at the 'Cache State' column and see when it changes to {}.

If you flush the 'settings' tag instead of 'users' at step 3, what happens to the cache?

A Cache is emptied

B Cache still contains the item

C Cache contains a different item

D Error occurs

💡 Hint

Since the item is tagged with both 'users' and 'settings', flushing either tag removes it.

Concept Snapshot

Cache tags group cached items by labels.
Use Cache::tags(['tag1', 'tag2'])->put(key, value, ttl) to store.
Retrieve with Cache::tags(['tag1'])->get(key).
Flush all items with a tag using Cache::tags(['tag1'])->flush().
Flushing a tag removes all items with that tag, even if they have other tags.

Full Transcript

Cache tags in Laravel let you label cached items with one or more tags. When you store an item, you specify tags. Later, you can retrieve the item by using any of its tags. You can also clear all cached items that share a tag by flushing that tag. For example, storing 'John' under key 'user_1' with tags 'users' and 'settings' means the item belongs to both groups. Retrieving with tag 'users' finds it. Flushing 'users' tag removes it from cache, even though it also had 'settings' tag. This grouping helps manage cache efficiently by clearing related items together.

Practice

1. What is the main purpose of using cache tags in Laravel?

easy

A. To group cached items for easy management and selective clearing

B. To encrypt cached data automatically

C. To increase cache storage size

D. To log cache hits and misses

Solution

1. Step 1: Understand cache tags concept

   Cache tags allow grouping of cached items under one or more tags.

2. Step 2: Identify the benefit of grouping

   This grouping helps to clear or manage all related cache items easily by tag.

3. Final Answer:

   To group cached items for easy management and selective clearing -> Option A

4. Quick Check:

   Cache tags = group and manage cache [OK]

Hint: Cache tags group items for easy clearing [OK]

Common Mistakes:

• Thinking tags encrypt data
• Assuming tags increase cache size
• Confusing tags with logging features

2. Which of the following is the correct syntax to store a cache item with a tag in Laravel?

easy

A. Cache::tags('users')->put('user_1', 'John', 3600);

B. Cache::put('user_1', 'John')->tags(['users'], 3600);

C. Cache::put('user_1', 'John', 3600)->tags(['users']);

D. Cache::tags(['users'])->put('user_1', 'John', 3600);

Solution

1. Step 1: Recall Laravel cache tag syntax

   The tags() method accepts an array of tags before calling put().

2. Step 2: Check method chaining order

   The correct order is Cache::tags([...])->put(key, value, time).

3. Final Answer:

   Cache::tags(['users'])->put('user_1', 'John', 3600); -> Option D

4. Quick Check:

   tags() before put() with array [OK]

Hint: Use tags() with array before put() [OK]

Common Mistakes:

• Passing tags after put()
• Using string instead of array in tags()
• Chaining methods in wrong order

3. Given the code below, what will be the output of Cache::tags(['products'])->get('item_1'); after Cache::tags(['products'])->flush(); is called?

Cache::tags(['products'])->put('item_1', 'Book', 600);
Cache::tags(['products'])->flush();
$value = Cache::tags(['products'])->get('item_1');
echo $value ?? 'Not found';

medium

A. Not found

B. CacheException

C. null

D. Book

Solution

1. Step 1: Understand flush() effect on tagged cache

   Calling flush() on a tag clears all cached items under that tag.

2. Step 2: Check retrieval after flush

   After flushing, get('item_1') returns null, so the null coalescing operator outputs 'Not found'.

3. Final Answer:

   Not found -> Option A

4. Quick Check:

   flush() clears tagged cache = 'Not found' [OK]

Hint: flush() clears all tagged cache items [OK]

Common Mistakes:

• Expecting cached value after flush
• Confusing flush() with forget()
• Assuming flush() only clears one item

4. Identify the error in the following Laravel cache tag usage:

Cache::tags('sessions')->put('session_1', 'data', 120);
Cache::tags(['sessions'])->flush();

medium

A. Missing cache driver configuration

B. Using string instead of array in tags() method

C. Calling flush() on tags is not allowed

D. put() method requires a closure

Solution

1. Step 1: Check tags() method argument type

   The tags() method requires an array of tags, not a string.

2. Step 2: Identify the incorrect usage

   Passing a string 'sessions' instead of ['sessions'] causes an error.

3. Final Answer:

   Using string instead of array in tags() method -> Option B

4. Quick Check:

   tags() needs array, not string [OK]

Hint: Always pass array to tags() [OK]

Common Mistakes:

• Passing single string instead of array
• Thinking flush() is disallowed
• Assuming put() needs closure

5. You want to cache user profile data and product data separately but clear both caches together when needed. Which is the best way to use cache tags in Laravel to achieve this?

hard

A. Tag user profiles with ['users'] and products with ['products'], then flush both tags separately

B. Use no tags and clear cache manually by keys

C. Tag both user profiles and products with ['app_data'], then flush this tag to clear all

D. Tag user profiles with ['users'] and products with ['products'], then flush(['users', 'products'])

Solution

1. Step 1: Understand grouping with tags

   To clear multiple cache groups together, use a common tag for both.

2. Step 2: Apply a shared tag

   Tag both user and product caches with a shared tag like 'app_data' to flush all at once.

3. Final Answer:

   Tag both user profiles and products with ['app_data'], then flush this tag to clear all -> Option C

4. Quick Check:

   Shared tag groups caches for joint flush [OK]

Hint: Use shared tag to clear multiple caches together [OK]

Common Mistakes:

• Flushing tags separately instead of shared tag
• Not tagging caches for group clearing
• Trying to flush multiple tags in one call incorrectly