PHP require_once error

Garrett

I am using CODA, MAMP and am working out of my HTdocs folder all locally. I am learning PHP and MVC structure and an coming across the following error when using require_once. I have read many of the other posts on this topic and no solution has worked.

The error I am receiving is:

Warning: require_once(UserModel.php): failed to open stream:
No such file or directory in - on line 13 Fatal error: require_once():
Failed opening required 'UserModel.php' (include_path='.:') in - on line 13

My file structure is:

database
----bdfdatabase.sql
index.php
UserModel.php

My code is as follows

<?php   
    require_once('UserModel.php');

    $dsn = "mysql:host=127.0.0.1;port=8889;dbname=bdfdatabase";
    $db_user= "root";
    $db_pass= "root";
    $model = new UserModel($dsn, $db_user, $db_pass);
    $rows = $model->displayUsers();

        foreach($rows as $row){
            echo "<h3><a href='details.php'>";
            echo "${row['user_name']}";
            echo "</a></h3>";
        }

?>

Any suggestions would be much appreciated.