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[2005-10-18 13:19 UTC] feldgendler at mail dot ru
Description: ------------ This is actually a bug in the well-defined and documented API, so there is no reproduce code here. After successfully establishing a connection, when an attempt to create another connection fails, there is no way to find out the errno. This is because mysql_errno() always uses an established link, either the one passed as the argument or the default one. There is just no way to find out why the second connection failed. // assume this one succeeds $first_connection = mysql_connect($host1, $u1, $p1); // at this point, $first_connection is the default link // assume this one fails $second_connection = mysql_connect($host2, $u2, $p2); // $second_connection is false, // $first_connection is still the default link echo mysql_errno(); // 0 is printed because there is no error // on $first_connection Before stamping "Bogus" on this bug, please note the following: 1. I have read the manual about mysql_errno() and mysql_connect(). Every word of it. Even more, I think that PHP currently behaves as documented. But it's just wrong because there is no way to find out why a connection has failed. 2. I have read other bug reports about mysql_errno(). They are actually about other issues, or they don't state this problem clearly enough, so I'm filing this bug report to make it clear what the problem is. 3. I have read the source code of the mysql extension. From the source, I've found out that the error code and message from a failed connection attempt is really stored in mysql_globals (connect_errno and connect_error), but mysql_errno() PHP function only returns MySG(connect_errno) when the function is invoked without arguments AND there is no default link. If there is a default link, and an attempt to establish a second one has failed, there isn't a way to have MySG(connect_errno) returned to the PHP program. It is not obvious how to fix this bug, because it isn't a deviation from the documented behavior, but rather an incompleteness of the API. Two of the possible approaches are proposed here: http://www.mail-archive.com/internals@lists.php.net/msg02524.html PatchesPull RequestsHistoryAllCommentsChangesGit/SVN commits
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About the patch: I think it's not enough. Once a connection attempt has failed, conect_errno will be nonzero, and mysql_errno() without arguments always will return this value. This will be too much deviation from the current behavior -- in fact, many always call mysql_errno() without arguments. Here is a typical script which will be broken: if (!mysql_connect('dbhost', 'user', 'pass')) { mysql_connect('backup-dbhost', 'user', 'pass'); } // ... if (!mysql_query("...")) { echo mysql_errno(); // This will print connect_errno! } I think that connect_errno should be reset to zero somewhere, but I don't know where it would be appropriate. mysql_errno() shouldn't reset connect_errno because mysql_error() and mysql_errno() are expected to be idempotent.The "easy" solution is to use mysqli without this default connection magic. Making this work doesn't look trivial as these two cases have to work: mysql_connect('localhost', 'valid', 'password'); mysql_connect('localhost', 'invalid', 'something'); mysql_query('invalid query'); echo mysql_error(); // should report the query error as well as mysql_connect('localhost', 'valid', 'password'); mysql_query('invalid query'); mysql_connect('localhost', 'invalid', 'something'); echo mysql_error(); // Should report the connect error Assigning to mysql team