指定时间的PHP file_put_contents [重复]

I have a php file that points to a url like so:

<?php
header('Content-Type: text/plain');
echo file_get_contents($_GET['url']);

The thing I would like my php file to do in addition to pointing to the URL is write a file to the server at a specific time each day -- let's say 6:00pm (18:00).

From my initial research, the write file part seems straight forward

file_put_contents('todaysDateData.txt', $_GET['url']);

However, figuring out how to call file_put_contents each day at a specific time is throwing me for a loop.

Question: Is it possible to write a file in the manner described above at a specific time each day in native php? Ideally I would like to name the file with today's date and "Data" suffix (i.e. Mar-29-2018.txt).

Edit

Going from the suggestions below, I have researched cron: I think the syntax for my use case is:

0 18 * * * path/to/my/command.sh

I think the date syntax is correct, but I'm still confused as to how cron is used with my php file. Should I change the sh file extension to php since I'm using file_put_contents? Or is this cron date thing going in my php file itself and I have to make a .sh (whatever that is?)

</div>

You can check timetamp and file name.

<?php

$todayHour = 18;
$todayMinute = 0;
$timeCreate = mktime($todayHour, $todayMinute, 0, date('m'), date('d'), date('Y'));
$todayFilename = 'data-' . date('Y-m-d') . '.txt';

if (time() >= $timeCreate && !file_exists($todayFilename)){
    // Code input content file here
    file_put_contents($todayFilename, $_GET['url']);
}