The version of PHP in use is 5.5.5 and I know this version of PHP can store precompiled script bytecode in shared memory, as mentioned in the following page: http://php.net/manual/en/intro.opcache.php
I also know OPcache can compile files as mentioned in the following page: http://php.net/manual/en/function.opcache-compile-file.php
Which would be great if this worked with Phar files. However, I can't tell whether PHP is loading my Phar files from bytecode in shared memory or not. I can't use the opcache_is_script_cached function to test because this is not available in PHP 5.5.5, the function is only available in PHP 5.6 and newer.
Could someone please clarify if this works or not, or at least explain to me how I can find out?
Yes it does. I won't go through the whole thing, but there is logic in ext/opcache/ZendAccelerator.c