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

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

This error arises when attempting to execute a MySQL query using mysqli_query(), but the provided parameter for the connection object is not a valid MySQLi object. The mysqli_query() function expects the first parameter to be an instance of the mysqli class.

In the provided code snippet, the error is likely caused due to the following reason:

Scoping Issue

The mysqli connection object $con, which is declared in the global scope, is not accessible within the getPosts() function. This results in the null value being passed as the first parameter to mysqli_query(), leading to the error.

Solution:

To resolve this issue, you can explicitly pass the connection object to the getPosts() function as a parameter. Here's the modified code:

function getPosts(mysqli $con) {
    $query = mysqli_query($con, "SELECT * FROM Blog");
    // ... Rest of the code remains the same
}

Now, when you call the getPosts() function, be sure to pass the connection object as an argument.

Additionally, it's a good practice to enable error reporting and handle database connection issues gracefully. Here's an example:

// Enable error reporting
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);

// Establish database connection
$con = mysqli_connect("localhost", "xxxx", "xxxx", "xxxxx");

// Check connection status
if (!$con) {
    throw new Exception('Failed to connect to MySQL: ' . mysqli_connect_error());
}

// Call the getPosts() function with the connection object
getPosts($con);

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