It's possible to set the cron job tool in my website cpanel 'VPS Hosting' to execute php file every 30 second I am using it to execute php file once at a minute *,*,*,*,* but I need to set it to run twice  in minute I have tried 1/2,*,*,*,* but it's not working.
Run A Cron Job Task Every 30 Seconds
cron;cpanel
Why don't you run a shell script which runs your command, like:#!/bin/tcsh -fstart:mycommand >> /tmp/outputsleep 30goto startAs someone else said, cron has a granularity of 1 minute.