Are you sure PHP was built/installed from source? You're running Red Hat aren't you? It may have been installed from RPM.
If you're not sure if you have installed by RPM you can find out by typing "rpm -qa |grep php". If you do have the RPMs installed, and you're trying to install by source, that may be one of your issues.
The RPM and the source installs put the binaries in two different locations. (/usr/local/bin/php for source and /usr/bin for the RPM). So, if you had the RPM installed and you ALSO installed from source, then typing 'php -v' into your shell may be picking up the wrong binary in your PATH even though you did get the new one installed.
On to the next step. Installing from source...
The easiest thing to do would be to take your current compile settings and reuse them with the new install. To find out everything you could want to know about the version of PHP currently being used by Apache, just put a file called "info.php" into your web directory and put this in it.
and then browse to that page. Two of the things you'll learn by doing this are the version being used by Apache and the configure string used when compiling. Use that string to rebuild the source and it should take effect without doing anything to Apache. Well, you MAY need to stop/start Apache to get it to take, but most of the time that isn't even necessary.
Please keep in mind that it IS possible to have two versions of PHP installed depending on your configure string. This being a different way to have two versions installed than I eluded to above. One version would be the DSO module that is being used by Apache (if you used with --with-apxs in your configure string) and the other being the binary version being used by your shell when you type 'php' on the command line.
This should get you started. I can help as much as you need me to, right up to setting up a remote session and walking through it with you. Let me know if you need anything else...