Question

Is it ok to use mysql_affected_rows to get the number of rows affected while doing an update by a user? What if there are several users updating their passwords and I need to know if each users update was successful or not. So if 3 users did updates simultaneously, mysql_affected_rows might return 2 even if one users update was not successful. Is that how it is? I cannot test with multiple users simultaneously. How safe is this.

Answer 1

It’s safe. It only returns data about the last query in your own connection.

PHP documentation (thanks to Fluffeh):

Get the number of affected rows by the last INSERT, UPDATE, REPLACE or DELETE query associated with link_identifier.

Since it’s a thin wrapper over MySQL C API, we can also check that:

my_ulonglong mysql_affected_rows(MYSQL *mysql)

It’s not explicitly said anywhere as far as I can see, but it does take the connection identifier and it seems that the general pattern is that all the functions return data about the specific connection:

Using LAST_INSERT_ID() and AUTO_INCREMENT columns simultaneously from multiple clients is perfectly valid. Each client will receive the last inserted ID for the last statement that client executed.

Anyways, it would be pretty unusable if you could not be sure whether the result you obtained is yours or not.