To date, there have also been 97 revenue generating print copies of the paperback sold and 60 digital Kindle editions sold. The majority of sales are through Amazon.com, generating a lot less income per book than copies sold through lulu.com.

• Total Revenue (all sources): $501.18
• Costs to create the book: ~$600
  (computer monitor, ISBN, review copies, office space rent, etc.)
• Hours spent writing: 175

In other words, with costs included, I’ve lost ~$100 creating the book. If that was not factored in, the hourly wage for creating the book so far would be $2.86/hour (in reality it is $0.00).

With over 8,000 downloads which are and will always remain free in PDF form, a donation of $1 for each download would have changed it to ~$33/hour. Would you consider purchasing a paperback PHP book copy today or donating to my hosting costs when downloading a free PDF of the PHP reference book? Thanks!