title: Make sure the cron job won't do the same job twice
body: <p>I've got a list of similar tasks in mysql database and a PHP-script that takes out 1 task at a time and executes it. When it's done it changes the flag from <strong>pending</strong> to <strong>done</strong></p>
  
  <p>I want to speed up my performance by adding more scripts(up to 20) running on the same database. How do i make sure these scripts won't be executing the same task twice, ie. processing the same row in the table</p>
  
  <p>Thanks in advance!</p>