If you have a server with PHP4 installed but need PHP5 on some websites then:
- Install a custom build of PHP5 to /opt/php5.
- Add lines like the following to your apache virtual host:
123AddHandler application/x-httpd-php5 .phpScriptAlias /bin /opt/php51/cgi-binAction application/x-httpd-php5 /bin/php5
You might also find the RemoveHandler directive handy to disable PHP4.