Why Does My `mysqli_query()` Function Receive a Null Value Instead of a MySQLi Connection Object?

Understanding "Warning: mysqli_query() expects parameter 1 to be mysqli, null given in"

In your quest to create a custom CMS, you may have encountered the dreaded error message: "Warning: mysqli_query() expects parameter 1 to be MySQLi, null given in." This frustrating problem often arises from a misunderstanding regarding the scope of variables within PHP functions.

Cause of the Error

The error suggests that your getPosts() function is attempting to access the $con variable, which stores your MySQLi connection object, but it's not accessible within that function's scope. This is because $con is defined outside of the getPosts() function.

Solution: Passing the Connection as Dependency

To resolve this issue, you need to pass the connection object to the getPosts() function as a dependency. By doing this, the function can access the connection and perform the necessary database operations.

function getPosts(mysqli $con) {
    // Code to query the database using $con
}

Preventing Further Errors

To minimize potential issues, consider using the following code to handle connection errors and throw exceptions:

mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT); // throw exceptions
$con = mysqli_connect("localhost", "xxxx", "xxxx", "xxxxx");

getPosts($con);

Additional Tips

• Use mysqli Object Directly: Avoid using mysqli_query() and opt for themysqli object's methods directly, such as $con->query().
• Handle Exceptions: Remember to handle exceptions thrown by the mysqli object using try...catch blocks to provide meaningful error messages.
• Dispose of Connections: Once you're done with the connection, close it using the $con->close() method to release resources.

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