Adds a cache entry only if its key does not already exist.
What Is apcu_add() in PHP?
Adds a cache entry only if its key does not already exist.
Its syntax is:
apcu_add(string $key, mixed $value, int $ttl = 0): boolParameters:
$key— Accepted as string; required argument.$value— Accepted as mixed; required argument.$ttl— Accepted as int; optional default 0.
Return type: bool. APCu must be installed and enabled. add() does not overwrite an existing item; CLI availability depends on apc.enable_cli.
Availability: Requires APCu enabled for the current PHP SAPI.
Example 1: Basic Usage
<?php
var_dump(apcu_add("guide:one", "Ready", 60));
Result: Results and availability depend on the current PHP process, system permissions, cache, filesystem or installed locale. APCu must be installed and enabled. add() does not overwrite an existing item; CLI availability depends on apc.enable_cli.
Example 2: A Different Input
<?php
var_dump(apcu_add("guide:one", "Replacement", 60));
Result: Results and availability depend on the current PHP process, system permissions, cache, filesystem or installed locale. APCu must be installed and enabled. add() does not overwrite an existing item; CLI availability depends on apc.enable_cli.
Practical Example: Applying It in a Program
<?php
$cacheKey = "settings:locale";
if (!apcu_add($cacheKey, "en_US", 300)) { echo "Value already cached"; }
Result: Results and availability depend on the current PHP process, system permissions, cache, filesystem or installed locale. APCu must be installed and enabled. add() does not overwrite an existing item; CLI availability depends on apc.enable_cli.
Important Behavior and Edge Cases
- Key behavior: APCu must be installed and enabled. add() does not overwrite an existing item; CLI availability depends on apc.enable_cli.
- Environment: Requires APCu enabled for the current PHP SAPI.
Comparison With Related Functions
| Function | Purpose |
|---|---|
apcu_add() | adds a cache entry only if its key does not already exist. |
apcu_store() | apcu_store() overwrites an existing cache entry; apcu_add() succeeds only when the key is absent. |
Common Beginner Mistakes
| Mistake | Correct Approach |
|---|---|
| Ignoring this behavior: APCu must be installed and enabled | APCu must be installed and enabled. add() does not overwrite an existing item; CLI availability depends on apc.enable_cli. |
Key Takeaways
- adds a cache entry only if its key does not already exist.
- APCu must be installed and enabled. add() does not overwrite an existing item; CLI availability depends on apc.enable_cli.
- Requires APCu enabled for the current PHP SAPI.
Summary: APCu must be installed and enabled. add() does not overwrite an existing item; CLI availability depends on apc.enable_cli.