中文与16进制互相转换

//字符串转换成16进制 
function str2hex($str){ 
$hex = ''; 
for($i=0,$length=mb_strlen($str); $i<$length; $i++){ 
$hex .= dechex(ord($str{$i})); 
} 
return $hex; 
} 
//16进制转换成字符串 
function hex2str($hex){ 
$str = ''; 
$arr = str_split($hex, 2); 
foreach($arr as $bit){ 
$str .= chr(hexdec($bit)); 
} 
return $str; 
}