Usted buscó: concurrent (Coreano - Inglés)

there is no support for indexes or memo fields. there is no support for locking, too. two concurrent webserver processes modifying the same dbase file will very likely ruin your database.
dbase files are simple sequential files of fixed length records.

most likely what has happened is, php 4 was compiled with the '--with-mysql' option, without specifying the path to mysql. this means php is using its built-in mysql client library. if your system is running applications, such as php 3 as a concurrent apache module, or auth-mysql, that use other versions of mysql clients, then there is a conflict between the two differing versions of those clients.
recompiling php 4, and adding the path to mysql to the flag, '--with-mysql= / your / path / to / mysql' usually solves the problem.