Which php version,ie php 4/5/6/7, should i learn for web development( layout, functionality, and CMS )?

Question

Which version should i learn, php 4, 5,6,7 to create websites with content management? And why.

Answer 1

PHP 5 is the current (5.3.2 at the time of writing), so that's what you should use. PHP 4 is old, and PHP 6 and 7 don't even exist as far as I know.

Answer 2

Well, to summarize :

• PHP 4 is not even maintained anymore -- not even for security problems -- since more than a year ; so, PHP 4 is not the way to go.
• PHP 5.2 (and PHP 5.3) is the way to go !
  • PHP 5.2 is stable, and every major PHP applications are compatible with it.
  • PHP 5.3 is stable, but not yet widely used (nor available on hosting services), and not all software are compatible with it yet -- but it will be the way to go soon (say one year, maybe) ; note that if you develop clean PHP 5.2 code, it'll work with PHP 5.3 too.
• PHP 6 is not even in alpha stage ; so it's far too early for it.
• PHP 7 is not even an idea.

Nowadays, we tend to use PHP 5.2 for existing projects, and/or applications that are to be released soon -- but more and more work is being done with PHP 5.3 ; for instance, the next major versions of the Symfony and Zend Frameworks will require PHP 5.3 (They should be relased this year).

EDIT 2010-03-27 : I should add that things seem to be moving, theses last few weeks, in the PHP 6 world...
See this blogpost, for example : Future of PHP 6