Inteteresting PHP generators behavior

generator.php

<?php

class TestGenerator {
    public function task1($doGenerate = true)
    {
        echo "Enter generator\n";
        if ($doGenerate) {
            echo "Generate values\n";
            yield 1;
            yield 2;
            yield 3;
            yield 4;
        }
        echo "Finally return\n";
        return 5;
    }

    public function task2($doGenerate)
    {
        echo "Delegate generator with return\n";
        return $this->task1($doGenerate);
    }

    public function task3($doGenerate)
    {
        echo "Delegate generator\n";
        $return = yield from $this->task2($doGenerate);
        echo "Where value $return ?\n";
        return $return;
    }
}

$obj = new TestGenerator();
echo "\nFirst test\n";
foreach ($obj->task3(true) as $val) {
    echo "Generator return value: $val\n";
}
echo "\nSecond test\n";
foreach ($obj->task3(false) as $val) {
    echo "Generator return value: $val\n";
}