PHP4 and PHP5 version conflicts and why we should stop using PHP 4

PHP 5 is in the market since many years, but it still has to capture the market.

Why? Is it not efficient version of PHP language?

What are main reasons behind slow-adoption of PHP version 5.

I am compiling a list of reasons; you can also send me the reason why you have moved to PHP5 or why you are not able to do that?

I will write about that list in my coming articles.