What is the difference between `mysqli_error()` and `error_log()` when handling MySQL errors?

`mysqli_error()` retrieves the specific error message returned by the MySQL server for a particular query. `error_log()` writes a message to the PHP error log, which is a general-purpose log for PHP errors, warnings, and notices. While `error_log()` can be used to log MySQL errors, `mysqli_error()` provides more specific information about the MySQL error. Using both is a good practice: `mysqli_error()` for detailed MySQL-specific errors and `error_log()` for general PHP issues.