mysqli_insert_id() expects parameter 1 to be mysqli, null given in

Question

This is connection string

global $db_connection;

$db_connection = false;

$db_connection = mysqli_connect($config['server'], $config['username'], $config['password'], $config['database']);

Function:

function lastInsertId() {
    return mysqli_insert_id($db_connection);
}

Getting error

mysqli_insert_id() expects parameter 1 to be mysqli, null given in ...

What could be the issue?

Answer 1

If you want to use a global variable for your mysql connection you must specify the variable with global for it to be usable in a function:

function lastInsertId() {
    global $db_connection;
    return mysqli_insert_id($db_connection);
}

Answer 2

You need function like:

function lastInsertId($db_connection) {
    return mysqli_insert_id($db_connection);
}
$db_connection = mysqli_connect($config['server'], $config['username'], $config['password'], $config['database']);
$id = lastInsertId($db_connection);

And when you are calling function pass connection object in argument.

EDITED : global function in php not working like they maybe works in other programming languages(eg. javascript). You must explicitly define global variable.

function lastInsertId($db_connection) {
    global $db_connection;
    return mysqli_insert_id($db_connection);
}