PHP is great for being able to easily create web apps that work. The problem is that it also easy to create code with major vulnerabilities that is a mess to read and try to audit. Many times PHP is used by desktop support technicians to create apps to track department inventory, or work orders that after a few years get coopted by the rest of the company and are being used at a scale never envisioned when the technician was copy/ pasting from a dummies book to make the code work.
Using includes you can reuse the same code in multiple scripts.
Logical Operators allow you to use AND or OR in comparisons for Loops and If Statements.