PHP7中的迭代器：如何高效地遍历和操作大规模数据集？

class ArrayIterator implements Iterator {
    private $arr;
    private $index;

    public function __construct($arr) {
        $this->arr = $arr;
        $this->index = 0;
    }

    public function current() {
        return $this->arr[$this->index];
    }

    public function key() {
        return $this->index;
    }

    public function next() {
        $this->index++;
    }

    public function rewind() {
        $this->index = 0;
    }

    public function valid() {
        return isset($this->arr[$this->index]);
    }
}

$myArray = [1, 2, 3, 4, 5];
$iterator = new ArrayIterator($myArray);

foreach($iterator as $key => $value) {
    echo "Key: $key, Value: $value
";
}

class FileIterator implements Iterator {
    private $file;
    private $line;
    private $current;

    public function __construct($file) {
        $this->file = fopen($file, 'r');
        $this->line = 0;
        $this->current = fgets($this->file);
    }

    public function current() {
        return $this->current;
    }

    public function key() {
        return $this->line;
    }

    public function next() {
        $this->current = fgets($this->file);
        $this->line++;
    }

    public function rewind() {
        fseek($this->file, 0);
        $this->line = 0;
        $this->current = fgets($this->file);
    }

    public function valid() {
        return !feof($this->file);
    }
}

$file = "data.txt";
$fileIterator = new FileIterator($file);

foreach($fileIterator as $lineNumber => $lineContent) {
    echo "Line: $lineNumber, Content: $lineContent
";
}