gistfile1.php

<?php

// custom array merging
// if something exists in the custom array, it should overwrite the default
// otherwise take the default value

$default = array(
	"key1" => "val1",
	"key2" => "val2",
	"key3" => array(
		"1" => "one",
		"2" => "two"
	),
	"key4" => "four"
);

$custom = array(
	"key1" => "val1",
	"key2" => "newval",
	"key3" => array(
		"1" => "one",
		"2" => "too"
	),
);

$result = merge($default,$custom);

function merge($a, $b) {
	$temp = array();
	foreach ($a as $key => $val) {
		if (array_key_exists($key, $b)) {
			if (is_array($val))
				$temp[$key] = merge($a[$key],$b[$key]);
			else
				$temp[$key] = $b[$key];
		} else
			$temp[$key] = $val;
	}
	return $temp;
}

/*
$result = array(
	"key1" => "val1",
	"key2" => "newval",
	"key3" => array(
		"1" => "one",
		"2" => "too"
	),
	"key4" => "four"
);
*/

?>

Ruby equivalent :)

default = {
"key1" => "val1",
"key2" => "val2",
"key3" => {
"1" => "one",
"2" => "two"
},
"key4" => "four"
}
custom = {
"key1" => "val1",
"key2" => "newval",
"key3" => {
"1" => "one",
"2" => "too"
}
}

result = default.merge custom

>> result

=> {"key1"=>"val1", "key2"=>"newval", "key3"=>{"1"=>"one", "2"=>"too"}, "key4"=>"four"}