问题：我需要一个UTF8“完全编码”的 XML文件;也就是说,没有实体代表符号,UTF8所包含的所有符号,除了仅有3个XML保留的符号外,“&amp;” (amp),“<” (lt)和“>” (GT).并且,我需要一个快速执行的内置函数：将实体转换为真正的UTF8字符(不破坏我的XML).
 PS：这是一个“现实世界的问题”(！);例如,在 PMC/journals,有数以万计的科学文章与 a special XML DTD相关(也被称为 JATS format)…要处理为“通常的XML-UTF8文本”,我们需要从数字实体更改为UTF8字符.

经过尝试的解决方案：此任务的自然功能是html_entity_decode,但它会破坏XML代码(！),转换保留的3个XML保留符号.

说明问题

假设

$xmlFrag ='<p>Hello World! &#160;&#160; Let A&lt;B and A=&#x222C;dxdy</p>';

实体160(nbsp)和x222C(双积分)必须转换为UTF8,而XML保留的不是. XML文本将(转换后),

$xmlFrag =’< p> Hello world！设A& lt; B和A =∬dxdy< / p>‘;

文本“A< B”需要XML保留字符,因此必须保持为A& lt; B. 沮丧的解决方案 我尝试使用html_entITy_decode解决(直接！)问题…所以,我将我的PHP更新到v5.5尝试使用ENT_XML1选项,

$s = html_entity_decode($xmlFrag,ENT_XML1,'UTF-8'); // not working
                                                        // as I expected

也许另一个问题是,“为什么没有其他选择去做我所期望的呢？” – 对于许多其他XML应用程序(！)而言,这对我来说非常重要.

我不需要解决方法作为答案……好吧,我展示了我的丑陋功能,也许它可以帮助你理解问题,

function xml_entity_decode($s) {
    // here an illustration (by user-defined function) 
    // about how the hypothetical PHP-build-in-function MUST work
    static $XenTITIES = array('&','>','<');
    static $XSAFENTITIES = array('#_x_amp#;','#_x_gt#;','#_x_lt#;');
    $s = str_replace($XENTITIES,$XSAFENTITIES,$s); 

    //$s = html_entity_decode($s,ENT_NOQUOTES,'UTF-8'); // any PHP version
    $s = html_entity_decode($s,ENT_HTML5|ENT_NOQUOTES,'UTF-8'); // PHP 5.3+

    $s = str_replace($XSAFENTITIES,$XENTITIES,$s);
    return $s;
  }  // you see? not need a benchmark: 
     //  it is not so fast as direct use of html_entity_decode; if there 
     //  was an XML-safe option was ideal.

PS：在this answer之后更正.必须是ENT_HTML5标志,用于转换really all named entities.

function xml_entity_decode($s) {
  // illustrating how a (hypothetical) PHP-build-in-function MUST work
    static $XENTITIES = array('&',$s); 
    $s = html_entity_decode($s,'UTF-8'); // PHP 5.3+
    $s = str_replace($XSAFENTITIES,$s);
    return $s;
 }

$countBchMk_MAX=1000;
  $xml = file_get_contents('sample1.xml'); // Big and complex XML string
  $start_time = microtime(TRUE);
  for($countBchMk=0; $countBchMk<$countBchMk_MAX; $countBchMk++){

    $A = xml_entity_decode($xml); // 0.0002

    /* 0.0014
     $doc = new DOMDocument;
     $doc->loadXML($xml,LIBXML_DTDLOAD | LIBXML_NOENT);
     $doc->encoding = 'UTF-8';
     $A = $doc->saveXML();
    */

  }
  $end_time = microtime(TRUE);
  echo "\n<h1>END $countBchMk_MAX BENCKMARKs WITH ",($end_time  - $start_time)/$countBchMk_MAX," seconds</h1>";