PHP Generator

Just a regular function, which yields things (but can return them sometimes as well).

Steps:

Create a function that yields things instead of `returns˙. If you need it to generate numbers, it should yield numbers. If you’re traversing a large file, it might yield lines, one by one.
Call the function, and store the result in a variable. Good job. This variable is now a generator. Every time there’s a yield in a function, calling it would result in a Generator object.
Use this generator in a loop, or manually as shown below, to perform some actions. Generators implement Iterator interface, which means they have access to all of the Iterator methods.
rewind can be thought of like this - start a new cycle, and call the code up until the first yield. It allows us to perform checks before trying to yield the value in our loops. rewind is not going to revert generator to the initial state. This is not possible with PHP generators.
It’s possible to return a value in your generator, using the return keyword. Result of the return can be fetched with getReturn() method. However, calling getReturn wen generator has not yet returned a value, would thron an exception.

function nrange($from, $to) {
    if ($from > $to) {
        throw new \Exception("Wrong range.");
    }
    for ($i = $from; $i < $to; $i++) {
        yield $i;
    }

    return 20;
}


$generator = nrange(0, 10);

$generator->rewind();

while ($generator->valid())
{
    $key = $generator->key();
    $value = $generator->current();

    // echo $generator->getReturn(); - will throw an exception as generator has not yet finished (no return value)

    echo $value . " ";
    $generator->next();
}

echo $generator->getReturn();

$generator = nrange(10, 1);
$generator->rewind(); // will throw an exception because of the range being wrong

Most common place where you’d use generators is for iteration over objects/values, but instead of hodling all of them in memory, they would be yielded one at a time.

You know I always wanted to pretend that I was an architect.

– George C.

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