Remove duplicate lines in a file

dedupLines.php

<?php
    $targets = array_slice($argv, 1);

    foreach ($targets as $target) {
        $map = array();

        foreach (explode("\n", file_get_contents($target)) as $line) {
            if (isset($map[$line]) === true) {
                continue;
            }

            $map[$line] = true;
        }

        file_put_contents($target, implode("\n", array_keys($map)));
    }