Note that the memory is lost after doing this. If you had a key 'foo' with a value of 1000 bytes, that 1000 bytes is lost, and the DB file size will reflect this.
(PHP 4, PHP 5, PHP 7)
dba_delete — Delete DBA entry specified by key
dba_delete() deletes the specified entry from the database.
TRUE on success or
FALSE on failure.