Why Am I Getting a 'mysqli Object is Already Closed' Error in My PHP Code?

mysqli::query(): mysqli Object is Already Closed / Couldn't Fetch mysqli Error

In PHP, an error message indicating "Couldn't fetch mysqli" typically occurs when trying to access a closed database connection. This commonly arises in object-oriented programming (OOP) scripts where the mysqli connection is closed prematurely.

Error Scenario

The provided code within class_EventCalendar.php throws the error due to the following issues:

1. Destructor Behavior: The __destruct() method closes the $DBConnect object when the EventCalendar instance is destroyed. This means that any subsequent queries attempted after the destruction will fail.
2. Query Execution: In the addEvent() method, the $DBConnect object is used to execute the SQL query. However, since the destructor closed the connection, the $DBConnect object is no longer usable.
3. DBConnect Parameters: Ensure that the @new mysqli() parameters are correct for your database server settings. In the example code, these parameters were modified from their original values.

Solution

To resolve this issue, consider the following:

1. Revise Destructor Logic: Modify the __destruct() method to only close the $DBConnect object if there are no remaining queries to execute. This will prevent premature closure of the connection.
2. Connection Error Handling: Handle connection errors gracefully in the database connection file using try-catch blocks or other error handling techniques.
3. PHP Version: The error "mysqli object is already closed" can also occur in PHP 8 due to changes in the handling of closed mysqli objects. Ensure that your PHP version is up-to-date.

Additional Troubleshooting Tips

• Use mysqli::error to check for the error message associated with the failed query.
• Ensure that the $_SESSION start is called before creating the mysqli connection object.
• Check the PHP script for any other instances where the mysqli connection is being closed prematurely.

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