[HTTP_ACCEPT_LANGUAGE en-US to en_US]

Need help with modifying current code to work with en_US instead of en-US and so on.

<?php
	// Languages we support
	// $available_languages = array("en", "en-us"); # old
        $available_languages = array("en", "en_US"); # new
	$default_language = "en"; // a default language to fall back to in case there's no match
	function prefered_language($available_languages, $http_accept_language) {
		global $default_language;
		$available_languages = array_flip($available_languages);
		$langs = array();
		preg_match_all('~([\w-]+)(?:[^,\d]+([\d.]+))?~', $http_accept_language, $matches, PREG_SET_ORDER);
		foreach($matches as $match) {
			list($a, $b) = explode('-', $match[1]) + array('', '');
			$value = isset($match[2]) ? (float) $match[2] : 1.0;
			if(isset($available_languages[$match[1]])) {
				$langs[$match[1]] = $value;
				continue;
			}
			if(isset($available_languages[$a])) {
				$langs[$a] = $value - 0.1;
			}
		}
		if($langs) {
			arsort($langs);
			return key($langs); // We don't need the whole array of choices since we have a match
		} else {
			return $default_language;
		}
	}
	$lang = prefered_language($available_languages, $_SERVER["HTTP_ACCEPT_LANGUAGE"]);
	print "<h3>Site available in:</h3><pre>";
	print_r($available_languages);
	print "</pre>\n<h3>Browser supported languages:</h3><pre>";
	print_r(explode(',',  $_SERVER["HTTP_ACCEPT_LANGUAGE"]));
	print "</pre>\n<h3>site will display in: <em>".$lang."</em></h3>";
?>

[Add date offset to current code]

Now its woking

<?php

class Time_zone {
    
    protected $regions = array(
        'Africa' => DateTimeZone::AFRICA,
        'America' => DateTimeZone::AMERICA,
    	'Antarctica' => DateTimeZone::ANTARCTICA,
    	'Artic' => DateTimeZone::ARCTIC,
    	'Asia' => DateTimeZone::ASIA,
    	'Atlantic' => DateTimeZone::ATLANTIC,
    	'Australia' => DateTimeZone::AUSTRALIA,
    	'Europe' => DateTimeZone::EUROPE,
    	'Indian' => DateTimeZone::INDIAN,
    	'Pacific' => DateTimeZone::PACIFIC
    );
    
    public function get_list() {
		
        $time_zones = array();
   	foreach ($this->regions as $name => $mask) {
			
	    foreach(DateTimeZone::listIdentifiers($mask) as $time_zone) {
	        $time_zones[$name][$time_zone] = '[UTC/GMT ' . $this->get_offset($time_zone) . '] ' . $time_zone;
	    }
			
	}
		
	return $time_zones;
		
    }
		
    protected function get_offset($time_zone) {
		
	$_tz = new DateTimeZone($time_zone);
        $_dt = new DateTime('now', $_tz);
        
        return $_dt->format('P');
		
    }
			
}

<?php
$time_zone = new Time_zone();
?>

<select>
<?php foreach($time_zone->get_list() as $region => $list) { ?>
    <optgroup label="<?=$region?>">
    <?php foreach($list as $time_zone => $name) { ?>
        <option value="<?=$time_zone?>"><?=$name?></option>
    <?php } ?>
    </optgroup>
<?php } ?>
</select> 

Output

<select>
    <optgroup label="Africa">
        <option value="Africa/Abidjan">[UTC/GMT +00:00] Africa/Abidjan</option>
	<option value="Africa/Accra">[UTC/GMT +00:00] Africa/Accra</option>
                         ...................................
    </optgroup>
    <optgroup label="America">
        <option value="America/Adak">[UTC/GMT -09:00] America/Adak</option>
	<option value="America/Anchorage">[UTC/GMT -08:00] America/Anchorage</option>
                         ...................................

[Add date offset to current code]

Testing code

$time_zone = new Time_zone();
?>

<select>
<?php foreach($time_zone->generate_list() as $region => $list) { ?>
  <optgroup label="<?=$region?>">
  <?php foreach($list as $name) { ?>
    <option value="<?=$name?>"><?=$name?></option>
    <?php } ?>
  </optgroup>
  <?php } ?>
</select>

Current output

<option value="[UTC/GMT +00:00] Africa/Abidjan">[UTC/GMT +00:00] Africa/Abidjan</option>

Expected output

<option value="Africa/Abidjan">[UTC/GMT +00:00] Africa/Abidjan</option>

[Add date offset to current code]

How do improve this class to output offset like + 02:00,  - 02:00

What i want to achieve is this output: [ UTC/GMT - 11:00 ] - Timezone name

class Time_zone {
	
    private $regions = array(
        'Africa' => DateTimeZone::AFRICA,
        'America' => DateTimeZone::AMERICA,
	'Antarctica' => DateTimeZone::ANTARCTICA,
	'Artic' => DateTimeZone::ARCTIC,
	'Asia' => DateTimeZone::ASIA,
	'Atlantic' => DateTimeZone::ATLANTIC,
	'Australia' => DateTimeZone::AUSTRALIA,
	'Europe' => DateTimeZone::EUROPE,
	'Indian' => DateTimeZone::INDIAN,
	'Pacific' => DateTimeZone::PACIFIC
    );
	
    public function generate_list() {
		
	$time_zones  = array();
	foreach ($this->regions as $name => $mask) {
	    $time_zones[$name] = DateTimeZone::listIdentifiers($mask);
	}
		
	return $time_zones;

    }
	
}

$tz = new Time_zone();
?>
<pre><?=print_r($tz->generate_list());?></pre>