Collect references to completed tasks

# Worker::collect

(PECL pthreads >= 3.0.0)

Worker::collect — Collect references to completed tasks

### 説明

public Worker::collect ([ Callable `$collector` ] ) : int

Allows the worker to collect references determined to be garbage by the optionally given collector.

### パラメータ

`collector`

  A Callable collector that returns a boolean on whether the task can be collected or not. Only in rare cases should a custom collector need to be used.

### 返り値

The number of remaining tasks on the worker's stack to be collected.

### 例

例1 A basic example of Worker::collect()

`<?php
$worker = new Worker();
echo "There are currently {$worker->collect()} tasks on the stack to be collected\n";
for ($i = 0; $i < 15; ++$i) {
$worker->stack(new class extends Threaded {});
}
echo "There are {$worker->collect()} tasks remaining on the stack to be collected\n";
$worker->start();
while ($worker->collect()); // blocks until all tasks have finished executing
echo "There are now {$worker->collect()} tasks on the stack to be collected\n";
$worker->shutdown();`

上の例の出力は以下となります。

    There are currently 0 tasks on the stack to be collected
    There are 15 tasks remaining on the stack to be collected
    There are now 0 tasks on the stack to be collected