Why php is throwing error when using dba_open for db4?

Question

I am trying to use db4 with php8.x

$cachefile = '/etc/cdata/cfile';
$dbh = dba_open($cachefile, "rl", "db4");

I am getting the error:

dba_open(/etc/cdata/cfile.lck): Failed to open stream: Permission denied

What am I doing wrong?

dba_open statement should execute successfully without warnings. I have changed owner of /etc/cdata folder to www-data:www-data (php version 8.2)