The extension is linked with Oracle client libraries 23.9 (Oracle Instant Client). For details, see Oracle's note "Oracle Client / Server Interoperability Support" (ID 207303.1).
You must install libclntsh.so.23.1 to use this package, provided by Oracle Instant Client RPM available from Oracle on: https://www.oracle.com/database/technologies/instant-client/downloads.html
Documentation is at https://php.net/oci8
Package built for PHP 8.5 as Software Collection (php85 by remi).