有点不懂这是怎么回事
<?php
use parallel\Runtime;
use parallel\Channel;
$thread_function = function (Channel $ch) {
echo "test1\n";
return;
$ch->send("test2\n");
};
$r1 = new Runtime();
$ch1 = new Channel();
$args = array();
$args[0] = $ch1;
$r1->run($thread_function, $args);
echo $ch1->recv();
$ch1->close();
PHP Fatal error: Uncaught parallel\Runtime\Error\IllegalReturn: return on line 3 of task ignored by caller, caller must retain reference to Future in D:\Desktop\test.php:18
请问如何在该函数中中断执行?