Description:
------------
When you interrupt iterations on "yield" generator via "break" instruction, 
generator function does not work out until the end of.

Test script:
---------------
<?php
$filename = '111111.txt';
$h = fopen($filename, 'w+');
for($i = 0; $i < 7; $i++) {
    echo 'write: ' . $i . PHP_EOL;
    fwrite($h, $i . PHP_EOL);
}
fclose($h);
function file_line_iterator($filename) {
    echo 'open file' . PHP_EOL;
    $h = fopen($filename, 'r');
    while(false !== $line = fgets($h)) {
        echo 'yield: ' .  $line;
        yield $line;
    }
    echo 'close file' . PHP_EOL;
    fclose($h);
}
$k = 0;
foreach(file_line_iterator($filename) as $k => $v) {
    echo 'iterate: ' . $v;
    if(++$k > 4) {
        break;
    }
}

echo 'exit' . PHP_EOL;
exit;

Expected result:
----------------
write: 0
write: 1
write: 2
write: 3
write: 4
write: 5
write: 6
open file
yield: 0
iterate: 0
yield: 1
iterate: 1
yield: 2
iterate: 2
yield: 3
iterate: 3
yield: 4
iterate: 4

* close file

exit


Actual result:
--------------
write: 0
write: 1
write: 2
write: 3
write: 4
write: 5
write: 6
open file
yield: 0
iterate: 0
yield: 1
iterate: 1
yield: 2
iterate: 2
yield: 3
iterate: 3
yield: 4
iterate: 4
exit