<?php
$input = $_POST['input'];
$output = $_POST['output'];
$replies = file('/this/is/where/my/file.is'); // I think I need to modify permissions on this file...
$found = false;
for ($i = 0; $i < count($replies); $i += 2) {
    echo $replies[i];
    echo '</br>';
    echo $replies[i+1];
    if (strcasecmp($input, $replies[i])) {
        $replies[i+1] = $output;
        $found = true;
        break;
    }
}

if (!$found) {
    array_push($replies, $input, $output);
}

$file = fopen('/this/is/where/my/file.is');
fwrite($file, join("\n",$lines));
fclose($file);

echo $input;
echo '</br>';
echo $output;
echo '</br>';
echo "Saved!";
?>