With PHP, you can run "php -m" from the command line for a list of
modules.
Alas, that only says that the dbx module is present. But I did find "php -i" is much the same as phpinfo() in a script which lead to yet another way of finding out if mysql support is present:
php -i | lynx -dump -stdin | grep -i mysql
And I still type "grep -y" now and again instead of "grep -i" :-)
I suppose the answer to the original question is "yes" since the Red Hat build includes mysql support and if you've got PHP installed then you've got mysql support in it.
jch