php 对数组按照字符串长度排序

$file = file('zong.txt');
usort($file,  'sortByLen');
$handle = fopen('zong2.txt', 'a');
foreach ($file as $v){

    fwrite($handle, $v);
}
fclose($handle);

function sortByLen($a, $b) {

    if (strlen($a) == strlen($b)) {

        return 0;
    } else {

        return (strlen($a) > strlen($b)) ? 1 : -1;
    }
}