I think I found the culprit:

/etc/php-8.1.conf contained this line:
extension_dir = "MODULES_DIR"

Instead of:
extension_dir = /usr/local/lib/php-8.1/modules

After correcting this it worked fine:
$ php-8.1 -v
PHP 8.1.32 (cli) (built: Mar 14 2025 07:05:24) (NTS)
Copyright (c) The PHP Group
Zend Engine v4.1.32, Copyright (c) Zend Technologies
    with Zend OPcache v8.1.32, Copyright (c), by Zend Technologies
$ 


> Am 15.03.2025 um 15:23 schrieb Mike Fischer <fischer+obsd@lavielle.com>:
> 
> After upgrading from php-8.1.31 to php-8.1.32 using `pkg_add -u`
> 
> I am encountering some PHP warnings I have not seen before:
> 
> $ php-8.1 -v
> PHP Warning:  Failed loading Zend extension 'opcache.so' (tried: MODULES_DIR/opcache.so (File not found), MODULES_DIR/opcache.so.so (File not found)) in Unknown on line 0
> PHP Warning:  PHP Startup: Unable to load dynamic library 'curl.so' (tried: MODULES_DIR/curl.so (File not found), MODULES_DIR/curl.so.so (File not found)) in Unknown on line 0
> PHP Warning:  PHP Startup: Unable to load dynamic library 'gd.so' (tried: MODULES_DIR/gd.so (File not found), MODULES_DIR/gd.so.so (File not found)) in Unknown on line 0
> PHP Warning:  PHP Startup: Unable to load dynamic library 'intl.so' (tried: MODULES_DIR/intl.so (File not found), MODULES_DIR/intl.so.so (File not found)) in Unknown on line 0
> PHP Warning:  PHP Startup: Unable to load dynamic library 'mysqli.so' (tried: MODULES_DIR/mysqli.so (File not found), MODULES_DIR/mysqli.so.so (File not found)) in Unknown on line 0
> PHP Warning:  PHP Startup: Unable to load dynamic library 'snmp.so' (tried: MODULES_DIR/snmp.so (File not found), MODULES_DIR/snmp.so.so (File not found)) in Unknown on line 0
> PHP Warning:  PHP Startup: Unable to load dynamic library 'zip.so' (tried: MODULES_DIR/zip.so (File not found), MODULES_DIR/zip.so.so (File not found)) in Unknown on line 0
> PHP 8.1.32 (cli) (built: Mar 14 2025 07:05:24) (NTS)
> Copyright (c) The PHP Group
> Zend Engine v4.1.32, Copyright (c) Zend Technologies
> $ 
> 
> The .so.so extensions seem strange. I checked the module names:
> $ ll /usr/local/lib/php-8.1/modules/                                                                                                              total 2162
>   2 drwxr-xr-x  2 root  wheel     512 Mar 15 15:04 ./
>   2 drwxr-xr-x  3 root  wheel     512 Nov  3  2023 ../
> 122 -rw-r--r--  1 root  bin    123312 Mar 14 14:07 curl.so
> 132 -rw-r--r--  1 root  bin    135024 Mar 14 14:07 gd.so
> 592 -rw-r--r--  1 root  bin    577400 Mar 14 14:07 intl.so
> 182 -rw-r--r--  1 root  bin    185544 Mar 14 14:07 mysqli.so
> 928 -rw-r--r--  1 root  bin    928640 Mar 14 14:07 opcache.so
>  38 -rw-r--r--  1 root  bin     36992 Mar 14 14:07 pcntl.so
>  70 -rw-r--r--  1 root  bin     71536 Mar 14 14:07 snmp.so
>  94 -rw-r--r--  1 root  bin     94736 Mar 14 14:07 zip.so
> $ 
> 
> And /etc/php-8.1/ contains:
> $ ll /etc/php-8.1/
> total 20
> 2 drwxr-xr-x   2 root  wheel   512 Nov  3  2023 ./
> 4 drwxr-xr-x  46 root  wheel  3072 Mar 15 15:05 ../
> 2 -rw-r--r--   1 root  wheel    18 Nov  3  2023 curl.ini
> 2 -rw-r--r--   1 root  wheel    16 Nov  3  2023 gd.ini
> 2 -rw-r--r--   1 root  wheel    18 Nov  3  2023 intl.ini
> 2 -rw-r--r--   1 root  wheel   250 Nov 18  2023 mysqli.ini
> 2 -rw-r--r--   1 root  wheel    26 Nov  3  2023 opcache.ini
> 2 -rw-r--r--   1 root  wheel    18 Nov  3  2023 snmp.ini
> 2 -rw-r--r--   1 root  wheel    17 Nov  3  2023 zip.ini
> $ cat /etc/php-8.1/*
> extension=curl.so
> extension=gd.so
> extension=intl.so
> extension=mysqli.so
> mysqli.default_socket = /var/www/var/run/mysql/mysql.sock
> zend_extension=opcache.so
> extension=snmp.so
> extension=zip.so
> $ 
> 
> Build bug or some bug in PHP?
> 
> 
> OpenBSD 7.6-stable amd64
> 
> Thanks!
> Mike

-- 
Mike Fischer
fischer@lavielle.com