PHP is a programming tool with a broad spectrum of applications, either alone or in combination with other tools for complex projects which call for more advanced programming.
Dynamic Web sites enable their owners to maintain and update the site themselves. Unlike static sites, for which programming experience is necessary, dynamic Web sites are designed for people without specialist skills.
These are an excellent solution for individuals and companies which need to be able to update information on their sites but do not want to engage a Webmaster to modify and update content. This drastically reduces maintenance costs.