PHP developers sometimes need to count object-keyed entries still present in a WeakMap. This comes up when preparing data, displaying results, or integrating information with other services.
The WeakMap::count() operation handles this particular task. The following examples show its result, its limitations, and a practical way to apply it.
What Is WeakMap::count() in PHP?
Count object-keyed entries still present in a WeakMap.
Its syntax is:
WeakMap::count(): int
The syntax shows the expected parameters and return type. Arguments marked with an ampersand are passed by reference and may be modified. Optional parameters control additional behavior; values must match the declared types.
Important: Entries disappear when their object keys have no other strong references. WeakMap values should not retain a strong reference to their own key.
Example 1: Basic Usage
This first example uses a small input to demonstrate the main result of WeakMap::count().
<?php
$map = new WeakMap(); $object = new stdClass(); $map[$object] = "cached"; echo $map->count();
Output:
1
The output demonstrates the primary operation: count object-keyed entries still present in a WeakMap.
Example 2: Understanding Another Case
This second example changes the input or option to reveal a different behavior of WeakMap::count().
<?php
$map = new WeakMap(); $object = new stdClass(); $map[$object] = 10; unset($object); echo count($map);
Output:
0
Compared with the first example, this one illustrates the same operation with a different input shape or option. Entries disappear when their object keys have no other strong references. WeakMap values should not retain a strong reference to their own key.
Practical Example: A Real Application Scenario
Here is a practical use of WeakMap::count() with realistic sample information. Adapt the values to match your application.
<?php
$map = new WeakMap(); $request = new stdClass(); $map[$request] = ["status" => "open"]; echo "Active entries: " . $map->count();
Output:
Active entries: 1
This is a useful starting point, but production code should check errors and validate values before performing the operation. Entries disappear when their object keys have no other strong references. WeakMap values should not retain a strong reference to their own key.
Important Behavior and Edge Cases
Entries disappear when their object keys have no other strong references. WeakMap values should not retain a strong reference to their own key.
- Input: Use the expected PHP types and validate user-provided values.
- Result: Check the return value separately from any modifications to the input.
- Environment: For extension, database, or filesystem examples, verify availability and handle failures before accessing results.
Comparison With Related Functions
| Function or Approach | When to Use It |
|---|---|
WeakMap::count() | Count object-keyed entries still present in a WeakMap. |
| Related functions | SplObjectStorage keeps object keys alive; WeakMap does not. |
Common Beginner Mistakes
| Mistake | Correct Approach |
|---|---|
| Confusing element count with nested item totals | Entries disappear when their object keys have no other strong references. WeakMap values should not retain a strong reference to their own key. |
| Counting before considering object lifetime or consumption | Check whether the collection holds references, has been consumed, or was modified. |
| Assuming count means the same thing for every container | SplObjectStorage keeps object keys alive; WeakMap does not. |
Key Takeaways
WeakMap::count()lets you count object-keyed entries still present in a WeakMap.- Entries disappear when their object keys have no other strong references. WeakMap values should not retain a strong reference to their own key.
- SplObjectStorage keeps object keys alive; WeakMap does not.
- Check input, return values, and environmental requirements when adapting the examples.
WeakMap::count() provides a focused PHP operation for count object-keyed entries still present in a WeakMap. Start with the simple examples, then adapt the practical example with the correct checks for your project.