Why is PHP free?

First, php can be cross-platform and can be guaranteed to be free. Server-side operating system will charge for using win, while asp can only run on win, and php can run on win or other platforms. If it is not free, it is free.

Second, php can cooperate with mysql, which is basically free. Of course, asp can also be used with mysql, but more often asp will be used with other databases, that is, there is a charge.

Third, php is not only php itself, but also a lot of extensible things. You can even modify php yourself to make it realize the functions you want. But asp is not. If you want to modify asp, hehe, closed source can only go to iis. If you want to modify or expand, sorry, it's not free.

Finally, you should know that none of win's office software is free. On the other hand, Php is open source and relatively free. Win's system is not free, but php can be cross-platform and doesn't have to run on Win.