在PHP中将utf8转换为latin1。255以上的所有字符都将转换为字符引用

我需要将UTF-8中的文本转换为ISO-8859-1中编码的文本，以便任何不属于ISO-8859-1集合的字符都将转换为字符引用。（例如

和#946；

）

示例：我想将文本转换为

hello é β 水

进入

我正在用PHP做这一切。我尝试了内置函数、iconv和TINDY以及它们的组合，但仍然无法得到可靠的解决方案

这是我到目前为止所拥有的

// convert any characters fount in the entity table into HTML entities
// do not double encode entities, do not mess with quotes
// use UTF-8 as character encoding because the page submits UTF-8
$str = htmlentities($str,ENT_NOQUOTES,'UTF-8',false);
//print $str."\n";

// convert text from UTF-8 to ISO-8859-1, 
// characters that cannot be converted will be converted to ?
$str = utf8_decode($str);
//print $str."\n";    

// make string XML valid.
// mainly it converts text entities into numeric entities.
$opts = array(  "output-xhtml"      => true, 
            "output-xml"        => true, 
            "show-body-only"    => true,
            "numeric-entities"  => true,
            "wrap"              => 0,
            "indent"            => false,
            "char-encoding" => 'latin1'
        );
$tidy = tidy_parse_string($str, $opts,'latin1');
tidy_clean_repair($tidy);
$str = tidy_get_output($tidy);      
//print $str."\n";

---

您将需要多字节支持。特别是：

---

（使用

htmlentities（'helloéβ）不会触及
水', ENT_COMPAT，'UTF-8'）
您至少可以将
é
和
β
转换为HTML实体（命名实体）。这就足够了吗？当然这还不够。最后一个字符是这里的主要问题。请注意，最终结果（XML数据）中不允许实体我希望ISO-8859-1设置为字符。非常感谢。我不知道我以前是如何没有注意到这些函数的。很遗憾，mb函数不是默认编译的一部分，因此并不总是在任何地方都可用。不过，我希望现在大多数服务器上都能看到它们。
// convert any characters fount in the entity table into HTML entities
// do not double encode entities, do not mess with quotes
// use UTF-8 as character encoding because the page submits UTF-8
$str = htmlentities($str,ENT_NOQUOTES,'UTF-8',false);
//print $str."\n";

// convert text from UTF-8 to ISO-8859-1, 
// characters that cannot be converted will be converted to ?
$str = utf8_decode($str);
//print $str."\n";    

// make string XML valid.
// mainly it converts text entities into numeric entities.
$opts = array(  "output-xhtml"      => true, 
            "output-xml"        => true, 
            "show-body-only"    => true,
            "numeric-entities"  => true,
            "wrap"              => 0,
            "indent"            => false,
            "char-encoding" => 'latin1'
        );
$tidy = tidy_parse_string($str, $opts,'latin1');
tidy_clean_repair($tidy);
$str = tidy_get_output($tidy);      
//print $str."\n";

$convmap= array(0x0100, 0xFFFF, 0, 0xFFFF);
$encutf= mb_encode_numericentity($utf, $convmap, 'UTF-8');
$iso= utf8_decode($encutf);