How to make SQL to a function [duplicate] - php

Question

This question already has answers here:
Reference: What is variable scope, which variables are accessible from where and what are "undefined variable" errors?
(3 answers)
Closed 4 years ago.
I am trying to make the following code to be a php variable. The idea is so I can get all the user data I need by giving the variable the id of the user.
$sql = "SELECT * FROM `users` WHERE user_id='$user_id'";
$result = $conn->query($sql);
if ($result->num_rows > 0) {
// output data of each row
while ($row = $result->fetch_assoc()) {
$displayname = $row['user_displayname'];
}
}
"display name" here is what I want to get.
It works when not in a function but it does not work in the function.
Perhaps I am doing something wrong, here. is how I am doing it.
function get_userdetails($user_id) {
// Figure out displayname of rulechanger
$sql = "SELECT * FROM `users` WHERE user_id='$user_id'";
$result = $conn->query($sql);
if ($result->num_rows > 0) {
// output data of each row
while ($row = $result->fetch_assoc()) {
$displayname = $row['user_displayname'];
}
}
}
Thanks in advance!

Answer 1

Presumably $conn is a global variable (object) representing your database connection. In order to access it inside a function you need to use the global keyword - in this case global $conn;
You will need to do the same with $displayname if you intend to refer to it outside of the function (after the function has set its value). Probably best here will be to simply return $displayname from your function.