Unable to compile PHP-7.3.0

I'm trying to upgrade to PHP 7.3.0 on a Fedora 25 server and I'm getting an error in the ./configure phase. Error: checking for U8T_DECOMPOSE... no configure: error: utf8_mime2text() has new signature, but U8T_CANONICAL is missing. This should not happen. Check config.log for additional information. Checking the log there are a number of places where there are fatal errors and the log says that compilation stopped, but the only errors related to mime2text are: (retrieved using "grep -i mime2text" so no context, sorry) configure:42106: checking for utf8_mime2text signature | utf8_mime2text(src, dst); | #define HAVE_NEW_MIME2TEXT 1 configure:42188: error: utf8_mime2text() has new signature, but U8T_CANONICAL is missing. This should not happen. Check config.log for additional information. ac_cv_utf8_mime2text=new Compiling certainly isn't my core skill, but I have no idea even where to start with this one. If necessary I can make the entire config.log available on my web site. Help would be appreciated! John