Procedural DI

<?php
class Config{

    private $_config = NULL;
    private $_filepath = NULL;

    public function __construct($filepath){
        $this->_filepath = $filepath;
        $this->load();
    }

    private function load(){
        if (is_array($this->_config))
            return;
        if (!file_exists($this->_filepath))
            throw new Exception('Configuration file not found');
        $this->_config = parse_ini_file($this->_filepath);
    }

    public function get($key){
        if ($this->_config === NULL)
            throw new Exception('Configuration file is not loaded');
        if (isset($this->_config[$key]))
            return $this->_config[$key];
        else
            throw new Exception('Variable ' . $key . ' does not exist in configuration file');
    }
}

#config instantiation
$config = new Config(ABSPATH . '/app/config.ini');

#Any function which uses config
function dbconnect($DBhost, $DBuser, $DBpass, $DBname){
    $db = mysqli_connect($DBhost, $DBuser, $DBpass, $DBname);
    if (!$db)
        throw new Exception('MySQL connection failed');
    else
        return $db;
}

try{
    dbconnect($config->get('DBhost'), $config->get('DBuser'), $config->get('DBpass'), $config->get('DBname'));
}catch(Exception $e){
    echo $e->getMessage();
}
?>