$string = "cfg_power";
$arr1 = str_split($string, 1);
foreach($arr1 as $akey=>$aval){
	$arr1[$akey]="0x".bin2hex($aval);
}
var_dump($arr1);

//16進位制ascii碼轉換成字元
$arr2 = $arr1;
foreach($arr2 as $skey=>$sval){
	$arr2[$skey]=chr($sval);
}

var_dump($arr2);
//字元轉化為字串
$arr3 = implode("",$arr2);
var_dump($arr3);

//16進位制ASCII轉化為字串
$arrs1 = array(0x63,0x66,0x67,0x5f,0x70,0x6f,0x77,0x65,0x72,0x62,0x79);

$myStr="";
for($i=0;isset($arrs1[$i]);$i++)
{
	$myStr.= chr($arrs1[$i]);
}
var_dump($myStr);