In the first part of a series on 'Building an Invoicing System', Leidago walks you through invoice management. If you are a freelance web developer, invoicing your clients for your paycheck at the end of each month,this application will help you manage your client details as well as your invoices, Leidago writes.

According to him, there are many invoicing systems out there, but most of them will cost you a lot of money. What you get with this system is:

• Client Management: create, update and view client information
• Invoice Management: create, update, view and print invoice data
• User Management: create and keep a log of people using your invoicing system

According to him, every person will have different requirements for an invoicing system, so he decided to make the program as general as possible. There are common aspects that everyone will need from an invoicing system, such as the ability to create a new invoice or to create a list of clients that you work with, among others. These commonalities are covered in the article.

He begins the article by creating a Login Script for a PHP Invoicing System. Leidago has an entire section devoted to 'What if I don't see that page?' where he explains that if the page is not present it means that the extension has not been enabled or cannot be found. In which case you should go back to the PHP site and download a version that includes the source, unzip the package and copy the extensions directory to your PHP directory. Then you should open up the php ini file, find the line that says extension_dir and add the location of your PHP directory to the line. He also explains database schema and login program.