Checks whether APCu holds one or several keys.
What Is apcu_exists() in PHP?
Checks whether APCu holds one or several keys.
Its syntax is:
apcu_exists(string|array $keys): bool|arrayParameters:
$keys— Accepted as string|array; required argument.
Return type: bool|array. For multiple keys the result is an array of keys that exist. A missing item and an item storing false are different cases.
Availability: Requires APCu enabled for the current PHP SAPI.
Example 1: Basic Usage
<?php
apcu_store("active", true);
var_dump(apcu_exists("active"));
Result: Results and availability depend on the current PHP process, system permissions, cache, filesystem or installed locale. For multiple keys the result is an array of keys that exist. A missing item and an item storing false are different cases.
Example 2: A Different Input
<?php
apcu_store("alpha", 1);
print_r(apcu_exists(["alpha", "missing"]));
Result: Results and availability depend on the current PHP process, system permissions, cache, filesystem or installed locale. For multiple keys the result is an array of keys that exist. A missing item and an item storing false are different cases.
Practical Example: Applying It in a Program
<?php
$keys = ["frontpage", "navigation"];
$present = apcu_exists($keys);
foreach ($keys as $key) { echo $key . ": " . (in_array($key, $present, true) ? "yes" : "no") . PHP_EOL; }
Result: Results and availability depend on the current PHP process, system permissions, cache, filesystem or installed locale. For multiple keys the result is an array of keys that exist. A missing item and an item storing false are different cases.
Important Behavior and Edge Cases
- Key behavior: For multiple keys the result is an array of keys that exist. A missing item and an item storing false are different cases.
- Environment: Requires APCu enabled for the current PHP SAPI.
Comparison With Related Functions
| Function | Purpose |
|---|---|
apcu_exists() | checks whether APCu holds one or several keys. |
apcu_fetch() | apcu_exists() checks key presence without retrieving a value; apcu_fetch() obtains the cached value. |
Common Beginner Mistakes
| Mistake | Correct Approach |
|---|---|
| Ignoring this behavior: For multiple keys the result is an array of keys that exist | For multiple keys the result is an array of keys that exist. A missing item and an item storing false are different cases. |
Key Takeaways
- checks whether APCu holds one or several keys.
- For multiple keys the result is an array of keys that exist. A missing item and an item storing false are different cases.
- Requires APCu enabled for the current PHP SAPI.
Summary: For multiple keys the result is an array of keys that exist. A missing item and an item storing false are different cases.