updated to 13.1 (i386). Apache won't run if php80 enabled

Since 12.3 is EOL, I upgraded to 13.1 yesterday on an i386 system.

I had php81 installed (and some web apps used it), but Apache
won't run if php is enabled in httpd.conf.

I have another machine running 13.1, but it's amd64.  It happily runs
Apache with php80, so I downgraded the i386 machine to php80
so the two machines would be "the same".

Except this didn't fix the problem.  Apache won't run with either php80
OR php81 enabled, using this stanza in httpd.conf:

LoadModule php_module         libexec/apache24/libphp.so

pkg info | grep php
mod_php80-8.0.28_1             PHP Scripting Language
php80-8.0.28_1                 PHP Scripting Language

pkg info | grep apache
apache24-2.4.56                Version 2.4.x of Apache web server

uname -a
FreeBSD dudley 13.1-RELEASE-p3 FreeBSD 13.1-RELEASE-p3 GENERIC i386

Am I doing something stupid?  (Wouldn't be the first time.)
How best to debug this?  A web search did not enlighten me.

Thanks,
Bill Dudley
New Jersey, USA
This email is free of malware because I run Linux.