Mine

<?php

$jimread = fopen("keywords.txt", "r");
$jimwrite = fopen("newkeys.txt" , "w");

while ($line = fgets($jimread)) {
    $line = rtrim($line);
    $line = preg_replace("/[^A-Za-z0-9 ]/", "", $line);
    fwrite($jimwrite, $line . "\r\n");
}

fclose($jimread);
fclose($jimwrite);
?>