php正则表达式用链接标记替换“某些单词”,但应在链接标记内排除“某些单词”

我有html内容存储在数据库表中.在那个html内容中我想用链接标签替换“SOME WORDS”.但如果“SOME WORDS”已经在链接标签中,我应该省略它们.

例如
内容

<p>Lorem ipsum dolor SOME WORDS, consectetur adipiscing elit. <a href="http://example.com">SOME WORDS</a> elementum pharetra velit at cursus. Quisque blandit, nibh at eleifend ullamcorper</p>

输出应该是

<p>Lorem ipsum dolor <a href="http://someurl">SOME WORDS</a>, consectetur adipiscing elit. <a href="http://example.com">SOME WORDS</a> elementum pharetra velit at cursus. Quisque blandit, nibh at eleifend ullamcorper</p>

如您所见,它应该在替换时排除现有的链接文本.

非常感谢一些指导,以进入正确的轨道.

解决方法:

这是使用DOMDocument而不是正则表达式来解决它的方法：

$contents = <<<EOS
<p>Lorem ipsum dolor SOME WORDS, consectetur adipiscing elit. <a href="http://example.com">SOME WORDS</a> elementum pharetra velit at cursus. Quisque blandit, nibh at eleifend ullamcorper</p>
EOS;

$doc = new DOMDocument;
libxml_use_internal_errors(true);
$doc->loadHTML($contents);
libxml_clear_errors();

$xp = new DOMXPath($doc);

// find all text nodes
foreach ($xp->query('//text()') as $node) {
        // make sure it's not inside an anchor
        if ($node->parentNode->nodeName !== 'a') {
                $node->nodeValue = str_replace(
                    'SOME WORDS', 
                    'SOME OTHER WORDS', 
                    $node->nodeValue
                );
        }
}
// DOMDocument creates a full document and puts your fragment inside a body tag
// So we enumerate the children and save their HTML representation
$body = $doc->getElementsByTagName('body')->item(0);
foreach ($body->childNodes as $node) {
        echo $doc->saveHTML($node);
}