There are lot ways to write a PHP program

• Vanillla PHP
• PHP program generators (like Form Generators or and Cloud hosting SiteBuilders)
• OHP CMS programs
• PHP Frameworks
• Using PHP libraries
• and more.

We can have

self hosting sites, where the user pays for hosting and maybe the maintenance like

• Web Sharind
• Cloud Hosting
• and more

apps from where we rent space + app, like WordPress multisite, where the user is not resposible for maintenance and backups.

• like tilda
• like wordprress.com
• like Wix
• and more

The most easy is the CMS sites (the popular WordPress), and after the PHP frameworks programming.

More difficulty means more money and more time.