Why Does `mysqli_query()` Return 'Warning: mysqli_query() expects parameter 1 to be MySQLi, null given'?

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

In your attempt to create a custom CMS, you encountered the following error message:

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

Cause of the Error

This error indicates that the mysqli_query() function, which executes SQL queries, expects a MySQLi object as its first parameter. However, in your getPosts() function, you are passing a null value instead of a MySQLi object.

Solution

The solution to this issue is to ensure that the $con MySQLi object is within the scope of the getPosts() function. In your code, $con is defined in the global scope, but it is not accessible within the function.

Passing the MySQLi Object as a Dependency

One way to address this is to pass the MySQLi object to the getPosts() function as a dependency. Here's how you can do it:

function getPosts(mysqli $con) {
    // etc
}

By making the MySQLi object a parameter of the function, you ensure that it is available within the function's scope and can be used by mysqli_query().

Additional Recommendations

In addition to resolving the scoping issue, consider implementing the following recommendations:

• Handle errors and connection failures by using mysqli_report() to set error reporting options.
• Stop script execution if a connection error or a query error occurs using mysqli::error().

Here's an example of how to implement these recommendations:

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

if (!$con) {
    throw new Exception("Failed to connect to MySQL: " . mysqli_connect_error());
}

getPosts($con);

By implementing these recommendations, you can ensure the robustness and reliability of your custom CMS.

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