php sleep and execute a function once

I have a question, I have a cron that runs every minute and calls a function, but that function needs to run wait for 20 sec and run again, that is, just twice

How can I put a sleep (20) and execute that function again, but only once

cron:
actualizar();

<?php
function actualizar(){
    //mis procesos
    //1
    //2
    sleep(20);
    //ejecutar actualizar() pero solo una vez mas
}
?>

Could you help me please

greetings