How is the type of function return value handled in PHP coroutines?

In PHP coroutines, the function return value type is a Generator object, containing the value generated by the yield expression. When a coroutine function executes and encounters yield , execution pauses and yield's value is returned, which is stored in the Generator object. When the coroutine function completes execution or a return is encountered, the Generator object completes and is closed, and the final return value can be retrieved from the coroutine function.

Handling of function return value types in PHP coroutines

In PHP coroutines, the return value type of functions is synchronized with The functions are slightly different. The coroutine function returns a Generator object, which contains the value generated by the yield expression during function execution.

Return value type processing mechanism

When the coroutine function is called, the PHP interpreter will create a Generator object. This object stores the function's state and the values ​​produced by any yield expressions.

During the execution of the coroutine function, each time a yield expression is encountered, execution will be suspended and the value of yield will be returned. The value will be stored in the Generator object.

When the coroutine function completes execution or encounters a return statement, the Generator object will complete and close. At this point, the final return value can be retrieved from the coroutine function.

Practical case

Consider the following coroutine function:

function getItems(): Generator
{
    yield 1;
    yield 2;
    yield 3;
}

When this coroutine function is called, it creates a Generator object. If we use foreach to iterate over this object, we can get the following results:

$generator = getItems();
foreach ($generator as $item) {
    echo $item . PHP_EOL;
}

Output:

1
2
3

In the above example, the coroutine function getItems() The return value type is a Generator object. foreach The loop will facilitate this object and obtain the value produced by the yield expression.

It should be noted that coroutine functions can also return other types of values, such as objects or arrays. As long as the returned value is an iterable object, you can use the foreach loop to iterate.

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