在PHP中将字符数组写入文件的最快方法是什么？

Say I have an array $arr and I want to write its contents to a file $handle. What's the fastest/most efficient way to do this in PHP(5)?

Some different options:

Convert the array to a string using implode:

$string = implode($arr);
fwrite($handle, $string);

Write it to the file char by char (seems like it would be slower to me):

foreach($arr as $char) {
    fwrite($handle, $char);
}

Concatenate using the . operator and then write:

$string = '';
foreach($arr as $char) {
    $string .= $char;
}
fwrite($handle, $string);

The third seems like it would be slowest to me, as I'm guessing that fwrite and implode are written in C... but then again with JIT-compiling these days maybe it's optimizing the concatenations with no function call overhead.

Which of these -- or some other way -- is the fastest and why?

Not sure about fastest/most efficient; but this opens the file, writes imploded data to the file and closes the file in one function:

file_put_contents('/path/to/file.txt', $arr);