如何在directadmin中使用cronjob运行php脚本

I'm new to cronjobs, had some classes in school, but the teacher didn't know a lot about it, wel.. i have write a script that delete users automatic when they are not-activated after 3 days, or not-active for 90 days.

But i like to run that script by cronjob... my host use Directadmin and i have used google a lot but nothing works... :(

I know how the timer works, but somewhere it goes wrong -,-

Maybe someone of you guys here can help me?

This is the line i use: /usr/bin/php -q /home/username/domains/Domain_name/public_html/folder/_dell.php

And here is the php script inside the _dell.php

BTW The php script works, when i run it my myself it run perfect (y)

<?php

    include "includes/conn.php";

    // Delete users die na 3 dagen nog niet zijn geactiveerd.
    $ongeactiveerd = time() - (60 * 60 * 24 * 3); // staat gelijk aan 3 dagen.
    $ongeactiveerd1=mysqli_query($server,"SELECT * FROM users WHERE rank < 1 AND status = 0 AND laatstgezien < $ongeactiveerd");

            if(mysqli_num_rows($ongeactiveerd1) > 0) { 

            $test = array();
                while($row = mysqli_fetch_array($ongeactiveerd1)) {

                    $test[] = $row['username'];
                }


                foreach($test as $testkey => $testuser) {
                    $test[$testkey] = "'".mysqli_real_escape_string($server,$testuser)."'";
                }

                $homo = join(', ', $test);

                echo $homo;

                $query = "DELETE FROM users WHERE username IN ($homo)";
                $query1 = "DELETE FROM pm WHERE verzender IN ($homo)";
                $query2 = "DELETE FROM pm WHERE ontvanger IN ($homo)";

                echo "<br>".$query."<br><br>".$query1."<br><br>".$query2;
                //exit();
                $result = mysqli_query($server,$query) or die (mysqli_error($server));
                $result1 = mysqli_query($server,$query1) or die (mysqli_error($server));
                $result2 = mysqli_query($server,$query2) or die (mysqli_error($server));

            } 
            else {
                echo "Er zijn geen on-geactiveerde gebruikers.<br><br>";
            }


        // Delete users die 90 dagen inactief zijn.
        $inactief = time() - (60 * 60 * 24 * 90); // staat gelijk aan 90 dagen || 3 maanden.
        $status1 = 1;
        $inactief1=mysqli_query($server,"SELECT * FROM users WHERE rank < 1 AND status = 1 AND laatstgezien < $inactief");

            if(mysqli_num_rows($inactief1) > 0) { 

            $test1 = array();
                while($row = mysqli_fetch_array($inactief1)) {

                    $test1[] = $row['username'];
                }


                foreach($test1 as $test1key => $test1user) {
                    $test1[$test1key] = "'".mysqli_real_escape_string($server,$test1user)."'";
                }

                $homo1 = join(', ', $test1);

                echo $homo1;

                $queryy = "DELETE FROM users WHERE username IN ($homo1)";
                $queryy1 = "DELETE FROM pm WHERE verzender IN ($homo1)";
                $queryy2 = "DELETE FROM pm WHERE ontvanger IN ($homo1)";

                echo "<br>".$queryy."<br><br>".$queryy1."<br><br>".$queryy2."<br>";
                //exit();
                $resultt = mysqli_query($server,$queryy) or die (mysqli_error($server));
                $resultt1 = mysqli_query($server,$queryy1) or die (mysqli_error($server));
                $resultt2 = mysqli_query($server,$queryy2) or die (mysqli_error($server));

            } 
            else {
                echo "Er zijn geen inactieve gebruikers.";
            }
?>