The main disadvantages of using persistent connections in PDO are:
Persistent connections do not automatically close at the end of a script execution. If a script fails to properly close a connection, it can remain open indefinitely, consuming database resources[1][3].
The connection state is not reset before reuse. For example, open and unfinished transactions are not rolled back, table locks are not released, and temporary tables are not dropped when a persistent connection is reused[1][4].
Persistent connections can cause issues with database connection limits. If the database has a limit on the number of concurrent connections, and that limit is exceeded by persistent connections from different PHP processes, some requests will fail to connect[1][3].
Debugging and diagnosing issues is more difficult with persistent connections. Problems may only occur after a specific sequence of requests using the same persistent con...
