Common Errors When Using MySQL Programs
Note: In older versions of PHP, the mysql extension does not support the authentication protocol in MySQL 4.1.1 and higher. This is true regardless of the PHP version being used. If you wish to use the mysql extension with MySQL 4.1 or newer, you may need to follow one of the options discussed above for configuring MySQL to work with old clients. The mysqli extension (stands for "MySQL, Improved"; added in PHP 5) is compatible with the improved password hashing employed in MySQL 4.1 and higher, and no special configuration of MySQL need be done in order to use this MySQL client library. For more information about the mysqli extension, see http://php.net/mysqli.
For additional background on password hashing and authentication, see Section 5.7.9, “Password Hashing in MySQL 4.1”.
4. Password Fails When Entered Interactively
Badly configured TCP/IP.
Faulty Ethernets, hubs, switches, cables, and so forth. This can be diagnosed properly only by replacing hardware.
The max_allowed_packet variable value is too small or queries require more memory than you have allocated for mysqld. See Section 9, “Packet too large”.
See also See Section 8, “MySQL server has gone away”.
11. The table is full
Common Errors When Using MySQL Programs