With PHP 5.6, oci_internal_debug() is a no-op, as documented on http://php.net/manual/de/migration56.extensions.php
(PHP 5, PHP 7, PECL OCI8 >= 1.1.0, PECL OCI8 <= 2.2.0)
oci_internal_debug — Enables or disables internal debug output
No value is returned.
Note:
This function was removed in PHP 8 and PECL OCI8 3.0.
With PHP 5.6, oci_internal_debug() is a no-op, as documented on http://php.net/manual/de/migration56.extensions.php