Is it worth upgrading php to accomodate new WP version?

[Ezpro9]

my client revisitors.com has a blog       blog.revisitors.com that we cannot update to a newer WP version 3.5.1 because his php version apparently must be upgraded first.

You cannot update because WordPress 3.5.1 requires PHP version 5.2.4 or higher. You are running version 5.1.6.

according to client it would be potentially hazarardous for him to upgrade the php

but we cant update or add new plugins because we arent running the current version of WP

what is worse?

i am responsible for his blog but i feel handicapped bigtime - at the same time i dont want him to do something that could wreck his site functionality either

any suggestions? or advice here?

thanks

[SVmedia]

Where does the potential hazard come in? Wouldnt there be more of a hazard in running out of date WP versions and server applications? Im no developer, but I'd say unless theres some older theme/plugin that requires a previous php or wp version, theres no risk to the site's functionality.

[Ezpro9]

this was clients exact reply:

The developers are skeptical about the possibility to update PHP on our server as this could seriously damage the entire RV site functionality

[TakeshiYoung]

It's always a good idea to keep Wordpress updated to the latest version. Because Wordpress is open source software, the code is available to everyone, which means hackers can use it to discover new vulnerabilities. Once hackers discover a vulnerability in a version Wordpress, they can easily target all blogs running that version to exploit that vulnerability.

The longer you go without updating Wordpress, the more you leave yourself vulnerable to getting hacked. You are going to have to update PHP and Wordpress eventually, so why not do it now?

[Ezpro9]

his developers say this:

The developers are skeptical about the possibility to update PHP on our server as this could seriously damage the entire RV site functionality

i have no clue why his site would be in jeopardy - he said he took care of any security issues by moving the blog to a subdomain from revisitors.com/blog to blog.revisitors.com

i also have no idea whether or not that makes his blog more secure but i need some in-depth professional advice here