Joomla PHP does not match host PHP

As others mention, Joomla does not install nor update PHP, it simply reports the version of PHP available.

It's possible that your .htaccess file contains instructions to set PHP version. This is quite common, but the exact code varies depending on your hosting company, but it usually looks something like this:

AddHandler application/x-httpd-php53 .php .php5 .php4 .php3

Look for this line in your .htaccess file, and comment it out (add # before the line) if you find it. Note that there can be several instances of .htaccess on your account, in different folders.

You can also check your PHP versions by creating a new .php file (call it anything you like), and put the following code inside to show information about your PHP settings:

<?php
    phpinfo();
?>

Save, and visit the file in your browser, (e.g. http://example.com/myphpinfo.php). Try moving the file to different folders, and see if the PHP version changes.

Make sure you remove the file when you're done testing, for security reasons.