title: How to check php job instance
body: <p>In my system, I've scheduled a PHP job to run each minute.</p>
  
  <p>Now I want that if 1 instance of this job is running and it takes more than 1 min, the new instance that starts after every minute checks if any previous instance is working and there is any previous instance running, the new one kills itself...I was trying the system() commands but cant figure it out.</p>
  
  <p>Any sugestions</p>