Best and simplest PHP insert to use wor WordPress

Excellent and best plugin for adding PHP to any page.
Pros:
Can use PHP as is. Does not require re-coding
Does not use a widget, which over-complicates and delays development.
PHP is stored in saved snippets for easy re-use of code.
Separates HTML from PHP for a clean quick assessment of what is where.
Carries form fields from one page to another
Sending emails is not interfered with in code
Allows other PHP functions.

Cons:
Sessions and database queries can be a bit tricky, but workable.