Four configuration directive scopes in PHP are follows as:
 
  PHP_INI_PERDIR
  PHP_INI_SYSTEM
  PHP_INI_USER
  PHP_INI_ALL

PHP users have a particularly useful trove of code at their disposal, made available through the PHP Extension and Application Repository, better known as PEAR. 

1.PEAR taking advantage of this community-driven service will save you countless hours of programming time. 
2.PEAR packages are available for accomplishing everything from creating barcode images,
 compressing files, abstracting database access, documenting code, and much more.

1.It's most effective for finding and reusing great PHP code.
2.Standard development guidlines are assured.
3.It offers more than 550 pakages catagorized under 37 different topics.

PHP uses two authentication variables as follows:

1. $_SERVER['PHP-AUTH-USER']
2. $_SERVER['PHP-AUTH-PW']
These variables store the username and password values respectively.

1.Shifts a major paradigm in development strategy.
2.Shifts the programs procedural events to real life entites.
3.Refocusing application data rather than it's logic.
4.It gives the fundamental concept for creating powerful programming model.