PHP - Application config file stored as - ini,php,sql,cached,php class,JSON,php array?

Question

I am trying to decide on the best way to store my applications configuration settings. There are so many options.

The majority of applications I have seen have used

Answer 1

Just an example of how to implement a central XML/Xpath configuration.

class Config {
    private static $_singleton;
    private $xml;
    static function getInstance() {
        if(is_null (self::$_singleton) ) {
                self::$_singleton = new self;
        }
        return self::$_singleton;
    } 
    function open($xml_file) {
        $this->xml = simplexml_load_file($xml_file);
        return $this;
    }
    public function getConfig($path=null) {
        if (!is_object($this->xml)) {
            return false;
        }
        if (!$path) {
            return $this->xml;
        }
        $xml = $this->xml->xpath($path);
        if (is_array($xml)) {
            if (count($xml) == 1) {
                return (string)$xml[0];
            }
            if (count($xml) == 0) {
                return false;
            }
        }
        return $xml;
    }
}

Example call

Config::getInstance()
    ->open('settings.xml')
    ->getConfig('/settings/module/section/item');