Thoughts on best way to test subdomain

index.php

<?php
/**
 *  how best to turn on errors for staging subdomains
 *
 *  as this is in the index.php, performance is important,
 *  although technically the page will be cached
 */

// 1. preg_match
if (preg_match('/^s1\.|^s2\.|^s3\.|^s4\.|^s5\.|^mac\.|^local\.|^mac-upgrade\./', $_SERVER['HTTP_HOST'])) {
    Mage::setIsDeveloperMode(true);
    ini_set('display_errors', 1);
}

// 2. in_array
$staging_subdomains = array(
    's1',
    's2',
    's3',
    's4',
    's5',
    'mac',
    'local',
    'mac-upgrade',
);
list($subdomain) = explode('.', $_SERVER['HTTP_HOST'], 2);
if (in_array($subdomain,$staging_subdomains)) {
    Mage::setIsDeveloperMode(true);
    ini_set('display_errors', 1);
}

// 3. strpos - THE ONE WE'RE GOING FOR
$staging_subdomains = array(
    's1',
    's2',
    's3',
    's4',
    's5',
    'mac',
    'local',
    'mac-upgrade',
);
foreach ($staging_subdomains as $needle) {
    if (strpos($_SERVER['HTTP_HOST'], $needle . '.') === 0) {
        Mage::setIsDeveloperMode(true);
        ini_set('display_errors', 1);
        break;
    }
}

// 4. remove strpos
$staging_subdomains = array(
    's1',
    's2',
    's3',
    's4',
    's5',
    'mac',
    'local',
    'mac-upgrade',
);
list($subdomain) = explode('.', $_SERVER['HTTP_HOST'], 2);
foreach ($staging_subdomains as $needle){ 
    if ($needle === $subdomain) {
        Mage::setIsDeveloperMode(true);
        ini_set('display_errors', 1);
        break;
    }
}

Version 2 benchmark http://codepad.viper-7.com/Isgmup