不需要序列化XML就可以将其加载到DOM或SimpleXML中。可以将其展开为DOM文档：

$reader = new XMLReader();
$reader->open(getXMLDataURL());

$document = new DOMDocument();

// navigate using read()/next()

while ($found) {
  // expand into DOM 
  $node = $reader->expand($document);
  // import DOM into SimpleXML 
  $simpleXMLObject = simplexml_import_dom($node);
 
  // navigate using read()/next()
}

但是，通过正确调用XMLReader:read()和XMLReader:next()，可以计算文档元素的子元素数量。read()将导航到包含后代的下一个节点，而next()将导航到下一个兄弟节点-忽略后代。

$reader = new XMLReader();
$reader->open(getXMLDataURL());

$document = new DOMDocument();
$xpath = new DOMXpath($document);

$found = false;
// look for the document element
do {
  $found = $found ? $reader->next() : $reader->read();
} while (
  $found && 
  $reader->localName !== 'LaunchBox'
);

// go to first child of the document element
if ($found) {
    $found = $reader->read();
}

$counts = [];

// found a node at depth 1 
while ($found && $reader->depth === 1) {
     if ($reader->nodeType === XMLReader::ELEMENT) {
        if (isset($counts[$reader->localName])) {
            $counts[$reader->localName]++;
        } else {
            $counts[$reader->localName] = 1;
        }
    }
    // go to next sibling node
    $found = $reader->next();
}

var_dump($counts);

function getXMLDataURL() {
   $xml = <<<'XML'
<?xml version="1.0" standalone="yes"?>
<LaunchBox>
  <Game>
    <Name>Violet</Name>
    <ReleaseYear>1985</ReleaseYear>
    <MaxPlayers>1</MaxPlayers>
    <Platform>ZiNc</Platform>
  </Game>
  <Game>
    <Name>Wishbringer</Name>
    <ReleaseYear>1985</ReleaseYear>
    <MaxPlayers>1</MaxPlayers>
    <Platform>ZiNc</Platform>
  </Game>
  <Platform>
    <Name>3DO Interactive Multiplayer</Name>
    <Emulated>true</Emulated>
    <ReleaseDate>1993-10-04T00:00:00-07:00</ReleaseDate>
    <Developer>The 3DO Company</Developer>
  </Platform>
  <Platform>
    <Name>Commodore Amiga</Name>
    <Emulated>true</Emulated>
    <ReleaseDate>1985-07-23T00:00:00-07:00</ReleaseDate>
    <Developer>Commodore International</Developer>
  </Platform>
</LaunchBox>
XML;
    return 'data:application/xml;base64,'.base64_encode($xml);
}

输出：

array(2) {
  ["Game"]=>
  int(2)
  ["Platform"]=>
  int(2)
}

听起来使用xpath而不是遍历XML可能适合您的用例，使用xpath可以选择您需要的特定节点：

$xml = simplexml_load_string($xmlStr);

$games = $xml->xpath('/LaunchBox/Game');

echo count($games).' games'.PHP_EOL;

foreach ($games as $game) {
    print_r($game);
}

https://3v4l.org/bLLEi#v8.2.3

我不确定我是否完全理解了您的要求，但如果您要寻找的输出是：

{ "Game":2, "Platform":2 }

那么您可以使用这个可流式处理的XSLT3.0样式表来实现它：

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
   xmlns:map="http://www.w3.org/2005/xpath-functions/map"
   version="3.0">
  
   <xsl:mode streamable="yes"/>
   <xsl:output method="json" indent="yes"/>
   <xsl:template match="/">
      <xsl:sequence select="fold-left(/*/*/local-name(), map{}, 
         function($map, $name){
           map:put($map, $name, 
             if (map:contains($map, $name)) 
             then map:get($map, $name) + 1 
             else 1)})"/>
   </xsl:template>
   
</xsl:stylesheet>

XSLT 3.0可以通过SaxonC产品中的PHP API获得（注意，这是我公司的产品）。

解决方案建立在巨人的肩膀上（感谢所有回复的人-- espeically @ThW）我使用了DOMDocument解决方案。随着时间的推移，我发现搜索文档以到达正确的起始点花费了很多时间。所以我循环了“while”以保持指针在正确的位置。这改变了传输时间，从4.当我从while循环中“中断”时，我返回到 AJAX 查询，然后更新屏幕并重新运行，直到我们导入了整个XML。

$reader = new XMLReader();
        $reader->open($xmlFile);

        $document = new DOMDocument();
        $xpath = new DOMXpath($document);

        $found = false;
        // look for the document element
        do {
          $found = $found ? $reader->next() : $reader->read();
        } while (
          $found && 
          $reader->localName !== 'LaunchBox'
        );

        // go to first child of the document element
        if ($found) {
            $found = $reader->read();
        }

        $counts = [];

        while ($found && $reader->depth === 1) {

            $currentElementKey++;

            if( $currentElementKey <= $positionInDocument ){
                // WE DON'T WANT THIS RECORD AS WE'VE ALREADY ADDED IT
                $reader->next();                
            }    

            if ($reader->nodeType === XMLReader::ELEMENT && $reader->localName == $sectionNameWereGetting) {

                // expand into DOM 
                $node = $reader->expand($document);
                // import DOM into SimpleXML 
                $simpleXMLObject = simplexml_import_dom($node);

                // TRANSFER OBJECT INTO ARRAY READY FOR DATABASE
                foreach($simpleXMLObject as $elIndex => $elContent){
                    $addRecord[$elIndex] = trim($elContent);
                }

                // MAKE ARRAY OF ARRAYS FOR DATABASE
                $allRecordsToAdd[] = $addRecord;
                // INCREMENT THE COUNT OF RECORDS WE'VE TRANSFERRED
                $currentRecordNumberTransferring++;
                // clearing current element
                unset($simpleXMLObject);

            }
            $positionInDocument = $currentElementKey;
            $reader->next();
            if( $currentRecordNumberTransferring >= $nextStoppingPoint ){
                // WE NEED TO STOP AND REPORT BACK

                \DB::disableQueryLog();              
                DB::table($dbTableName)->insert($allRecordsToAdd);
                $allRecordsToAdd = array();

                $loopTheWhileForSpeed++;
                if( $loopTheWhileForSpeed < $maxLoops ){
                    $nextStoppingPoint = self::calculateNextAjaxStoppingPoint($currentRecordNumberTransferring, $totalNumberOfRecords, $maxRecordsAtATime);           
                } else {
                    break;
                }

                
            }

        }

    $documentStats["positionInDocument"] = $positionInDocument;
    $documentStats["currentRecordNumberTransferring"] = $currentRecordNumberTransferring;

    $reader->close();
    unset($reader);
    unset($document);
    unset($xpath);

    return  $documentStats;