<?php
 
function _config($for=null)
{
 
    $path    = dirname(__FILE__) . '/config.xml';
    $sig     = md5($path);
 
    if (defined($sig))
    {
        $config = unserialize(constant($sig));
    }
        else
    {
        $config  = (object) array();
        $xml     = simplexml_load_file(dirname(__FILE__) . '/config.xml');
 
        foreach ($xml->environments->children() AS $env)
        {
            $environment              = $env->attributes()->name;
            $config->{$environment}   = (object) array();
 
            foreach ($env->children() AS $variable)
            {
                $config->{$environment}->{$variable->attributes()->name} = (string) $variable;
            }
        }
 
        define($sig,serialize($config));
    }
 
    if ($for==null)
    {
        $for = getenv('ENVIRONMENT');
 
        if (empty($for))
        {
            $for = 'dev';
        }
    }
 
    return isset($config->{$for}) ? $config->{$for} : (object) array();
 
}

<?xml version="1.0" encoding="UTF-8"?>
 
<config>
 
    <environments>
        <environment name="dev">
            <variable name="mysql_host">localhost</variable>
            <variable name="mysql_port">3306</variable>
            <variable name="mysql_user">root</variable>
            <variable name="mysql_password">root</variable>
            <variable name="mysql_database">portal</variable>
        </environment>
    </environments>
 
</config>

function flatten_array($array, $parents = '')
{
	if ( !is_array($array) AND !is_object($array))
	{
		return array($parents . $array);
	}
 
	$array  = (array) $array;
	$flat 	= array();
 
	foreach ($array AS $k => $v)
	{
		if (is_numeric($k))
		{
			$k = '';
			$p = $parents;
		} else
		{
			$p = $parents . $k . '.';
			$flat[] = $parents . $k;
		}
 
		$flat = array_merge($flat,flatten_array($v,$p));
	}
 
	return $flat;
}

$array = flatten_array(array(
	"fruits"  	=> array(
		"a" 		=> "orange",
        "b" 		=> "banana",
        "c" 		=> "apple"
    ),
    "numbers" 	=> array (
		1, 2, 3, 4, 5, 6
	),
    "holes"   	=> array (
		"first",
        5 			=> "second",
        "third"
    )
));
 
echo implode('\n',$array);

fruits
fruits.a
fruits.a.orange
fruits.b
fruits.b.banana
fruits.c
fruits.c.apple
numbers
numbers.1
numbers.2
numbers.3
numbers.4
numbers.5
numbers.6
holes
holes.first
holes.second
holes.third