gistfile1.php

<?php

class LineIterator {
    protected $handle;
    public function __construct($file) {
        $this->handle = fopen($file, 'r');
    }
    public function __invoke() {
        return fgets($this->handle);
    }
}

$iterator = new LineIterator('/etc/hosts');
while($line = $iterator()) {
    echo $line;
}