title: automatic number increase in php based web form
body: <p>So I have created an html form which then posts the results to a php file that overlays them on a PDF and then emails that PDF to myself and the email that was put in the form. All I want to do now is find a simple way to make it so that the PDF includes a sequential number.  </p>
  
  <p>For example: When the form is filled out for the first time the number 0001 is input automatically into the PDF and 0002 for the second time and so on. </p>
  
  <p>Is there an easy PHP function to accomplish this? </p>
  
  <p>Essentially I am creating an online invoicing form so when I do service calls I can create an invoice on the spot from a web browser which is then emailed to my office and the client.  </p>
  
  <p>Any help would be greatly appreciated. </p>