PHP shm_put_var() stores a serializable PHP value under an integer key in shared memory. The examples below show how the call behaves, where it is useful, and which limitations matter.
What Is shm_put_var() in PHP?
Stores a serializable PHP value under an integer key in shared memory.
Its call structure is:
shm_put_var($shm, $key, $value)The arguments identify the values or resources passed to shm_put_var(). Read the examples with attention to the type of each supplied argument and to whether the function modifies its input or returns a separate result.
Requires the corresponding System V shared-memory or SHMOP extension and suitable operating-system support. IPC keys used below are illustrative; use coordinated, environment-appropriate keys in real deployments.
Example 1: Basic Usage
This example introduces shm_put_var with a direct call and a small, readable input.
<?php
$memory = shm_attach(0x12421, 4096, 0600);
if ($memory !== false) { shm_put_var($memory, 1, "ready"); shm_detach($memory); }Stores a serializable PHP value under an integer key in shared memory. Objects and serialized values come with size and trust considerations; avoid storing untrusted deserialized objects.
Example 2: Another Behavior or Input
Compare this input with the previous example: changing the data or option can affect how shm_put_var behaves.
<?php
$memory = shm_attach(0x12422, 4096, 0600);
if ($memory !== false) { shm_put_var($memory, 2, ["count" => 4]); shm_detach($memory); }The changed input illustrates why output may differ with the chosen values or environment. Objects and serialized values come with size and trust considerations; avoid storing untrusted deserialized objects.
Practical Example: Using the Feature
The following example incorporates shm_put_var into a workflow. Values such as paths, connection handles and configuration options must come from trusted application settings.
<?php
$memory = shm_attach(0x12423, 4096, 0600);
if ($memory !== false) { if (!shm_put_var($memory, 5, ["updated" => time()])) { error_log("Write failed"); } shm_detach($memory); }In a real application, check each operation result, validate values before use and clean up acquired resources. Objects and serialized values come with size and trust considerations; avoid storing untrusted deserialized objects.
Important Behavior and Edge Cases
- Purpose: Stores a serializable PHP value under an integer key in shared memory.
- Key limitation: Objects and serialized values come with size and trust considerations; avoid storing untrusted deserialized objects.
- Failure handling: Check return values and handle invalid inputs and unavailable operating-system or extension features where relevant.
Comparison With Related Functions
| Function or Approach | Best Fit |
|---|---|
shm_put_var() | Stores a serializable PHP value under an integer key in shared memory. |
shm_get_var() | Reads a value stored under an integer key; shm_has_var() only checks whether the key exists. |
Common Beginner Mistakes
| Mistake | Correct Approach |
|---|---|
| Objects and serialized values come with size and trust considerations; avoid storing untrusted deserialized objects. | The correct approach depends on this behavior: Objects and serialized values come with size and trust considerations; avoid storing untrusted deserialized objects. |
| Ignoring errors or cleanup after the operation. | Validate inputs and check each result; close files, restore settings or release resources when the operation requires it. |
Key Takeaways
- Stores a serializable PHP value under an integer key in shared memory.
- Objects and serialized values come with size and trust considerations; avoid storing untrusted deserialized objects.
- Use the examples as starting points, and adapt environmental paths, resources and permissions rather than assuming fixed results.
shm_put_var is useful when its specific behavior fits the problem. The safest implementations combine the correct API with input validation, error checking and resource cleanup.